to me similar to maybe a crushed MSContin 100mg. Maybe a bit less....like 80mgs and a bit different of a feel.
That's for the brand you can buy at most supermarkets....not to be named!
I should also mention that 100mg of MsContin will feel 'cleaner' than PST. I put this down to the absence of other alkaloids, especially codeine. If I do the tea I know I'm in for a lot of nose, testical and head scratching.....not so with morphine. I use both regularly and alternate, so I think the guide you gave was quite accurate (60-100mg). In my experience, I would say that for the batches of seeds I have had, it NEVER felt stronger than 150mgs of oral crushed MSContin. I know I will get an ear-bashing from the mods but for me the range is not that wide (as I use the same, most-commonly available seeds each time). I'd give a mean value of 90mgs if I had to for all my experiences. (many many of 'em) with some outliers to the lower side and virtually none to the upper side.
I have had various forms of opium in Laos, too, and somewhat 'pride' myself on being an expert in this field

Opium feels cleaner a high than PST, too, which kind of doesn't make much sense. The range of potency has clearly been far larger for opium in my experience as I procurred it from different sources (as opposed to the same seeds here in Oz every other week) Pitch black, reeking opium is the best. If it's quite moldable like play-dough then it is cut with a lot of fats and quite weak in my experience. When offered I started declining that variety on my trips.
I did come across seeds in Laos, too, and I would have to say they were sticky, reeked, and were quite black. I would assume they are a lot more potent compared to what comes through to our shores. In my experience I have NEVER seen seeds here in Oz that looked like them - completely unwashed, with bits and pieces of straw mixed in, sticky.... even at Indian grocers etc. Perhaps customs has some form of mandatory processing for seeds...who knows.