OK so in fact parents who want their kids to be able to communicate with them as needed, not parents who want their kids to be able to play video games when so desiring?

Of course the ability to do the first gives the ability to do the second, but I think we can agree that they don't as a general rule want their kids to play video games. Again, outliers always exist.

Now as to why parents want their kids to answer when texted that can vary, maybe a lot of reasons are stupid but I can easily construct familial situations where the kid not being able to answer a text is a major disaster and probably parents in that situation flip shit because stuff is way more difficult for them than it is for other people. Probably those parents should have notified the school though, and the school should allow exceptions, but lots of schools are not, in my experience, run by people able to see the need for exceptions.

So I sort of expect that flipping shit happens the more stress there is, some of that can be passive aggressive shit flipping to relieve stress from other places but I would expect, as it matches to my experience in the world, that when shit flipping over trivial stupid stuff happens it is probably because the relatively trivial situation that is being flipped over connects closely to some problematic situation, and thus the trivial situation for most people who flip shit over it is not as trivial as it might be for the general population.

In short I would expect that the tendency to flip shit over the kid not being able to answer calls or texts in class would be proportionate to how absolutely necessary it is for particular family to have the kid answer calls or texts.