Ok so my experience is totally different from yours. I honestly find my schoolmates annoyingly active, some are always busy filling up their schedule with club activities or stupid random events, some are always studying and are extremely aggressive and demanding during lectures/seminars. Maybe at your school(s) the students are all zombies. Let's just agree to disagree.
I don't see how it is bizarre to be shy when you're 18. It's an awkward age, and the environment is completely new in comparison to what you're used to just a few months ago. Maybe the primary and secondary education is at fault here, Idk, personally I think it's totally normal and I hate it when some people are overly excited about everything.
And it even makes more sense during a language course as not everyone is comfortable speaking an unfamiliar language.
Finally you're overestimating the powers of Taiwanese parents. Yes there are lots of extremely controlling parents, I know some of those and yes their kids are miserable, but I know way more people whose parents are nothing like what you described, or they are, but the kids never buy their shit.