Passkeys can absolutely constitute two factors. At least the iOS and Android default implementations back user verification (which the website/relying party can explicitly request) with biometric authentication, which together with device possession makes them two factor.

Someone gotta tell all these SaaS about that if so, because currently everyone is treating Passkeys as an alternative to 2FA. Take a look at how GitHub handles it for example when you use TOTP, they'll ask you to replace TOTP with passkeys.