Now, I think that if they re-released the actual, O.G. P1 or P2, people would go bonkers for it, but that's just wishful thinking on my part
That was what Japan's Shuku 20 Shunen Tamagotchi (something like "Celebrate! 20th Anniversary Tamagotchi") line from November of 2017 was - a very-slightly-tweaked re-issue of the P1 and P2.
I imported a P2 version because I never had a P2 back in the day, and the little changes (less-scheduled misbehaviour, sickness, and pooping, plus snacks carrying an actual health risk because overdoing them in the child stage leads to an early death) shake things up just enough to make things fresh, without being too far removed from what made the originals great and therefore spoiling the original formula.
It's a massive shame that they haven't released these outside of Japan - as you say, people would absolutely flip for them.
If you want one, I believe that Japan You Want might have some more at the moment. They certainly did when I checked there a few days ago.
I DO count parents who had a Tamagotchi when they were younger and are buying a Mini for their kid as the "nostalgia market" though, because their decision is based on "oh I had one of those and loved it as a kid, maybe my kid will enjoy it too."
I sort of do, too, honestly, but I also sort of don't because whilst that's a parent's or grandparent's reason for buying, the experience for the recipient is new.
It's an annoying borderline thing that I'm never quite sure how to categorise.
But yeah, it does sit further on the nostalgia-market side, you're right.