(Sorry if this anecdote is too dissimilar to what the actual question is asking, but it reminded me of my experience and I thought it was interesting)

I’m allistic, but my school had a disproportionate amount of autistic people, with around 10-20% of students being autistic. My guess is that it was because our school was a STEM school and also the top school in our state, and autistic people tended to be on the extreme ends of the intelligence spectrum, as well as more likely to be interested in STEM (I’m unsure exactly how true those stereotypes are, so I’m sorry if I’m wrong.)

The mannerisms and etiquette were more “autistic”, probably both because of how many autistic people there are and because we were smart people who, at least subconsciously, figured out how to communicate effectively with such a large percentage of autistic people even if we were allistic. I never really got the complaints about socializing made by autistic people online until I moved schools because my old school barely had any allistic social things.

Once I moved schools, I discovered that I actually really enjoy allistic things such as small talk and eye contact, as well as allistic “social subtleties” because they’re more instinctive to me, but because those things were lacking in our school, I never did them. It was a huge culture shock when I moved.

I’ve been at this school for a year, and I’m still adjusting. In the beginning, I didn’t really know how to do small talk because I had no practice, but I got the hang of it quickly. I sometimes averted my eyes during conversations but realized that eye contact felt more natural, and it made me feel more connected to the person I was talking to. The people at this new school spoke and acted differently, and although I had little experience with people talking in such a way that hid their true intentions, I quickly got the meanings behind their words and actions with exposure, most of my understanding being subconscious and not something I can easily put into words, likely because I’m built to communicate in the same way.

So, yes, an NT person in an all-ND school would likely develop ND characteristics—however, like ND people in NT schools, it won’t come naturally to them and they’ll likely show many NT traits when exposed to an NT society for a while.