Well, they're synchronized to my Apple account so that's not an issue. They're available on all of my Apple devices, or even ones I don't have right now that I log into in the future

Plus, none of the sites that I use passkeys for would I be locked out. They all have account recovery procedures just like if I forgot my password. And, finally, for the important ones like my Google account (where my email lives) I have other non-Apple devices like a Yubikey setup as additional Passkey/FIDO authenticators