Their ToS also classifies Crypto-Mining, farming or plotting (whatever that is) as grounds for cancellation.
Also everything forbidden by German law results in a cancellation. So if you would have for example posted something before 2017 about a state leader that might seem like an insult your server might be gone. ( https://www.loc.gov/item/global-legal-monitor/2017-07-26/ger... )
Make sure you avoid p2p stuff that scans for other servers on the hetzner network, too, even if it's legitimate and not infringing on copyright. They won't ban you right away, but their systems will detect it and give you 24h to confirm you're not infected with malware before shutting down the server. For IPFS or Bittorrent, you should be able to use it for legitimate purposes after blocking the local IPs.