Little bit funny to say the least, how can you overstay if you're not staying over?! Ok I understand, it's up to the Immigration officer you have in front of you. Anyway, do you know if it is possible to cancel your extension when you come back to Thailand (after one year), going to Immigration with a letter from the school, without being fined?
Asymptomatic quarantine hotel scenario: I think your doubts are legitimate, for what I've understood in this scenario AXA is paying just for your medical treatments, but not for your hotel costs. In case of asymptomatic quarantine at hospital they pay it in full? Please let us know if you get more details from the insurance company because it's still not clear to me. Hotels here :
The METV is useless at the moment I think, how would you think to use it? You cannot easily border run. The STV is mostly advised against if you do your research.