They may not block them by "default" but when all the onion browsers automatically have a high threat score for not running cloudflare's invasive javascript it's the same thing. Especially combined with the high "threat score" they attribute to almost all out node IPs. I don't even use tor and they still block my browser when I'm trying to read science journal articles because my browser cannot run their bleeding edge features they use in their spying javascript.

And everyone knows it because that's what the lived experience of trying to access cloudflare blocked sites on tor browser (or any other browser that's not made by a megacorp). It doesn't matter what cloudflare's intentionally ambiguous and probably disingenuous wording might try to imply. The only people who think otherwise have never actually tried using tor to surf the web.