Nope. Individual customer setting, not a Cloudflare policy. We work closely with the Firefox team on many projects.
It's (literally) basic logic
1. Some site flags Firefox. 2. Not all sites flag Firefox. 3. Either every site flags Firefox or individual sites flag Firefox. 4. It is not true that every site flags Firefox (obverse of 2) C. Individual sites flag Firefox (disjunction with 3, 4)