That's a very common description of hitting puberty, so witnessing this in 7th grade specifically doesn't demonstrate your claim.
I lack the domain knowledge to evaluate the evidence against the null hypothesis, so you may well be correct — you just haven't actually demonstrated it with your anecdote.
Hide in room, grunt when asked questions, moody, "disrespectful to their elders", that kind of thing is all "less social".
Although I can think of one specific context where I would say "shy" for a bit: suddenly developing a new axis of emotional drives (lust) that they have to learn to navigate socially.
I see what you’re saying, but this was an anecdote by the 7th grader in relation to their peers. Sure puberty makes teenagers not want to interact with their parents, but I’ve never heard it make them not want to interact with their classmates—usually the opposite.
I lack the domain knowledge to evaluate the evidence against the null hypothesis, so you may well be correct — you just haven't actually demonstrated it with your anecdote.