It's still just (mostly) ketamine.
The longer you take a drug the more your brain and body just start to somewhat adapt to the affects to adhere to the inevitable if slightly fucked and messy-functioning homeostasic drive, and as such the subjective effects change. This is the case even with taking long breaks, it's just inevitable. Equally the brain changes continuously over time in slightly mysterious ways and thus particularly with certain classes of psychoactives, probably, where the subjective effects are already hard to define, describe or even remember, they genuinely do induce slightly different changes depending when you take them in your life, and even the smallest chemical difference in balance of neurotransmitters or distribution of receptors can equate to a disproportionately enormous difference in the subjective effects.
For dissociatives there's the added touch of fuckery in that you really never properly remember exactly how you felt on any given dissociative episode, IMO/IME, you just kinda piece it together from fragments and retroactively fill in the blanks and splice bits together while trying to assemble your memory, it's good enough but over time all the lil uncertainties, discontinuities, and recall-errors that get garbled into your general sense of a given experience start to add up and progressively skew your expectations as to what you should feel next time, or, really, what you ever felt any time.
I'm on some kinda half-assed drawn out mostly totally sober drug abstinence thing recently, but for whatever reason ketamine I still keep coming back to now and then although I've dramatically dropped my annual gram-consumption total since just a few years back. But I'm pretty confident I know roughly the caliber of ketamine supply you're probably also exposed to. Without getting unnecessarily explicit in sourcing details either I don't really get K these days from people or places who talk about "speedy K" or stuff like that BUT honestly I'm pretty sure I kinda still know what they mean and I'm pretty sure I know essentially what you mean by that. But it just isn't really a description that means very much of anything. Heck yesterday was my last big K day out of the year and out of just a couple this year lol and I definitely felt a good amount of the time that the K I had could be described as "speedy", but it was also in some ways pretty damn sedating since as always I spent the vast majority of the time sitting spangled in the same general area while thinking I was traversing all kinds of abstract spaces and now and then other rooms in other places with other people talking to me and thinking I was engaged in a conversation with some people via a bluetooth earbud when in actual fact I was most likely just jabbering nonsense over some random autoplayed YouTube video I'd put on before I slipped off the edge of the cliff of relative awareness of reality into just pure spangleverse for a while.
It definitely wasn't quite what I was expecting out of it, what I wanted to get out of it, although right now I don't know what either of those things really were exactly, although in another sense I guess I just wanted to touch that delicious incomprehensible and all-encompassing strangeness (dare I say it, "vastness" lol) again, and in that sense it definitely was that... as I suppose it kinda always is, even if it's absurdly difficult to really pin down.
Was it a bit different to past experiences I've had? Yeah, for sure. Was it unexpected? In many ways yeah. Do I think that's because it was anything other than ketamine? Absolutely not...
Everything I've ever said in response to these kinda questions, which pop up all the time, and not just about ketamine, although I guess I have more to say about ketamine, more of a frame of reference to it, knowledge and experience of it, etc etc... IMO still applies. And this isn't necessarily true for all other drugs where people wonder "what's with X drug these days that I thought used to mostly make me feel like this but now somehow makes me feel different?", of course, SOMETIMES it can legitimately be to do with cuts, analogues, and the like where that drug just ISN'T what it's being sold as... but with ketamine, AFAIK there still isn't a good economic, chemical, practical or rational reason to think that - in the most general sense, in the area you mentioned, most of the time what's being sold as ketamine, and feels, generally, like ketamine - is anything other than just ketamine.
