Totally unprofessional and a complete joke. Will never use them on a production system again. Always angry if they are mentioned here like they are a legitimate choice...
Your case sounds like one of your IPs got blocked in their firewall, which can happen if you use bittorrent or receive a DMCA strike. But then other IPs associated with the domain would still work fine.
That said, yes, their abuse team is rather trigger happy. I've had disagreements with them, too. They can be VERY German ;) But in general, calling them on the phone can fix these cases within minutes.
i think giving 2 days before turning anything off would be sensible. 1 day would still be ok. but turning it off immediately without even giving a chance to reply is not acceptable. especially since anyone can send a trademark complaint without providing any evidence. so, if you want to do some domain sniping, look for businesses hosted on hetzner and watch them go down...
Generally, I would recommend not hosting APIs on the primary domain for exactly that reason - it's too easy to be hit with some sort of complaint and have that domain cut off (DMCA, preliminary injunction, SPAM complaint against your mail server, shitty host, ...).