"A better version of password syncing" is exactly what Passkeys are and ought to be. Just like passwords, but unphishable, unguessable, not reusable across sites, not vulnerable to data breaches, and with better UX.

Stranding private keys in clone resistant secure enclaves has unacceptably bad UX for the average user, which is why very few implementations try to do that.

> at which point it’s no different to password syncing

You still get the phishing resistance, though!