In your case, with a strain that can produce sclerotia they would probably start producing those. So to be clear: that's truffles like "philosopher's stones". They should be in the dark for that though. Your hydroshroom fruiting chamber apparently has light but as I understand it you let them colonize in the dark which is good.
If you let them colonize for too long the more light there is present the worse it is, because it will take any such bit of light as a signal to start fruiting. Again, if you have a sclerotia producing species apparently the tendency to fruit is lower so less of an issue. You don't want that for a couple of reasons: the fruits cannot really grow in the jars because there is no real refreshed air and no space so most if not all will become 'aborts'. Which are mini shrooms that have stopped growing. You need to be alert for those because they can start rotting after that and ruin the rest. Having aborts on the side and bottom of your colonized substrate is a common problem for this same reason, even with birthed cakes or layed trays.
When you see 'pinning' meaning very tiny mushrooms that start to form like match heads only smaller... thats the sign for you to birth the cake. With bird seed I would instead just make sure that every kernel is white colonized and add 3 extra days for consolidation, then open it up.
You can opt for dunking and rolling with cakes, dunking is putting a colonized cake in a pan or container of water and submerging it - then setting it in the fridge for a day for it to soak up water. After that the rolling means literally rolling your cakes in vermiculite to make it stick to the wet sides. Then that serves as a layer (like a casing layer) as well, to protect from contamination and regulate water. You can mist the vermiculite with a water spray, but should not apply water to the mycelium directly or else it can rot. Even if not, an excess of water will make the mycelium stop growing locally and even retreat away from the patches of water.
So: 95-100% air humidity YES, but liquid water directly touching the fungus NO. With air humidity the water is dissolved in the air, makes all the difference.
By the way here is a picture of aborts or advanced stage pinning inside the jar:
Aluminum foil is not casing. Casing means a top layer of a soil material mix that has very little nutrients but can contain and give off lots of water. As a water reservoir the mushrooms can draw from that and become bigger. Another function of the casing is to keep contaminants from falling directly onto the mycelium and attacking it for food. With casing, they fall on that and since there are not many nutrients they cannot really grow there. Your mycelium will form a very loose fuzzy blanket through the casing, looking a bit like clouds. I guess this is a hyphae system that only serves as something like plumbing for the water absorption.
So the aluminum foil is not like casing at all, aluminum foil would only be a cover. I used aluminum covers in the time when I had just crumbled my cakes into trays and put a casing layer on it of like half an inch to three quarters. I punched little air holes in the aluminum, and periodically checked to see if the fuzz would cover the casing and start looking ready to pin, then apply a light signal.
What you can do is let bird seed colonize, preferably shaking them loose from each other periodically but not too often because every time you do it the mycelium needs time to reconsolidate. Then when all is colonized and relatively loose and still granular, you can use (again sterilized!!) trays for example those cheap aluminum low barbecue/oven trays. Pay attention not to fill them up, leave 1 1/2 inches above the rim or something.
Then cover the colonized birdseed with casing. A good casing material is something like a mix of coco coir + vermiculite or sphagnum moss + vermiculite, either of which is sterilized and made wet with sterile water by using something like a sterilized plant sprayer. That way you can make it wet without reaching a point where its soaking. Soaking is not good! THAT is what casing is, a layer of fuzzy stuff. Google those things like coco coir, vermiculite and sphagnum moss if you don't know it. And check the Shroomery for gods sake there are thousands of descriptions of it and pictures. I have told you so many times before to put in some own energy and do research there.
Because usually substrate jars are filled too far up so there is very little room for mushrooms to grow. I have seen people growing mushrooms inside the jars themselves but mostly for novelty. Other than that it's just not a very ideal way of working. Bags are not supposed to be filled that heavily, unless your plan with it is to do what is called "spawn to bulk", or lay in trays. You need bags with a filter patch by the way, a special piece in it that allows air exchange. The same goes for jars, you can make that yourself with holes cut in the lids and a piece of tyvek... but I never did that. I just bought filter boxes which are plastic instead of glass jars, and the lids of those boxes have great pre-made filter patches for air exchange.
Pinning can take like a week or two after you have placed it in the tray or put the cake in the fruiting chamber.
B+ is a strain of pretty good growers, and advised for starters and all-round enthousiast. Maybe not extremely special like Penis Envy or Albino strains but they get the job done. I also liked Cambodians as well.
But you shouldn't focus on the variation between growing properties of different Cubensis substrains. Look up lists and descriptions of lots of commonly found substrains and from the ones listed as "easy" to grow, pick one that sounds nice to you.
Something you should realize most of all is that there is not really one superstrain that colonizes fast and agressively and is strong against contamination and pins quickly and grows fast and in abundant numbers and into large sized fruits. You can't have it all. Strains are typically specialized in some of these characteristics but not others. The main difference I would focus on is if you want lots of small mushrooms or only 3 or 4 very large ones, or something in between. And well okay, being known for rapid and strong colonization like lots of substrains from South-America such as the Amazonian / PES amazonian... that's also worth considering.
Other than that, the differences are just really not that big and what result you get from a single specific substrain can vary a lot by the way you grow them. Many differences as portrayed by distributors are for a significant part marketing ploys. Not entirely, but sometimes it can appear as if all these Cubensis substrains are all completely special and different, as different as different species. Well they're not, they are all types of Cubensis. Errr well except for a number of mutants that have been propagated of course.
Please next time you come back with questions show that you have tried searching for answers instead of just immediately asking.
On the bright side, if we continue like this - it's almost like cultivation FAQ or something hehe.