Right. So 'fixated on the nomenclature.' A psion is person who focuses on developing and using psionic powers. Presumably the psionic sorcerer is exactly that.
We've seen the rules twice now. Unless they've been drastically changed the second time, this is not the case. The previous times they were a Sorcerer who cultivated some vaguely Far Realm/Psionic-themed abilities/spells, rather than someone who was using "psionic powers". They're no more a psion than a Draconic-origin Sorcerer is a dragon.
I actually agree with this. I wish there was more focus on subtle, non-flashy magic. But this really doesn't depend on psionics rules being distinct, there being bespoke psion class or even psionics existing as a concept. It just requires there to be plenty of non-flashy spells and classes that can choose those spells. So I'd assume the new mind-affecting spells will help there.
I mean, I agree with what you're saying but a major bar is the slot system, and the limited number of slots classes provide.
The slot system causes most spells to be designed in a very specific way - they either are non-concentration, and do a "one-off", often very major effect, or they're concentration, and they offer some kind of continuous effect, which is also typically pretty major. It's not just a matter of flash, it's a matter of scale. And the number of slots you have is very limited, and using higher-level slots for lower-level spells is often extremely wasteful (this improved a bit in 5E, but it's still pretty extreme). And each spell tends to be extremely confined in what it does (there is the odd exception).
I was thinking about this a bit, and I feel like what you really need for psionics is sort of more developed cantrips, almost, or cantrips you can "boost" somehow to have larger effects. Most of the more subtle magic in these books is cantrip-like, in that it's typically at will, but it is also often possible to vary the power, and sometimes to do amazing things. That doesn't work well with the design of spells present in the slot system.
The sad thing is, 5E isn't a million miles away from being able to do something like this well. It really would just need a spell-point rather than slot system, and more spells which scale, and probably some reconsideration of concentration. I don't think it'll happen short of 6E, though.