If 90 or 95% of their traffic comes from a single domain (and presumably has for a while), that still doesn’t make OP sound guilty. If there was a legal issue Cloudflare legal should’ve stepped in, not their sales team.
That was the part that bugged me. This workflow is very busted from a user standpoint, though I'm sure it works very nicely to Cloudflare!
It smells like the "problem" was detected by automation, but instead of being able to reach anyone technical to work through it, you can only call sales teams.