Apple Sign-In is just an OpenID federated login; these don't inherently provide any anti-automation or rate limiting; they just push the problem to the Identity

Apple Sign-In is just an OpenID federated login; these don't inherently provide any anti-automation or rate limiting; they just push the problem to the Identity Provider. IdPs like Apple/Google/Microsoft might do a fine job of limiting you to "one account per $unit-of-hardware"; Apple in particular can do this via iOS attestation. But then you're limited to either their heuristics (in the case of MSFT/Google) or their hardware (in the case of Apple). Ultimately this is apples-to-oranges, though, since Cloudflare is not offering an IdP product but simply an anti-automation solution. If you use federated auth, you're getting (and giving up) a lot of other stuff beyond just anti-automation.