Now I realise it:
j. Infrastructure Integrity
We reserve the right to delete, suspend, or terminate your access to, or ability to use, any and all Services that we determine to be placing undue strain on our infrastructure. These changes were made in response to ping services on Glitch and our efforts to make the site more stable.
Even if you don’t ping your projects, you just need to “place undue strain” on the servers to make it against the ToS.
I’m being spammy to send this message