If you read the parent post, the support is implemented on top of WebAuthn standard, so as far as developers are concerned, they don’t have to do anything Safari-specific to support it - their code will work fine with YubiKey or other Authenticators as well. Which is the point of web standards after all.
Safari may support Face ID and Touch ID, but I doubt it would be in anybody else's best interest to also support it.
Not that it matters anyway, since on iOS they all use Safari...