I thought the point of passkey security is that you don't have to send the private key around, it can stay on your device. Different passkey per device. Lose or destroy a device, delete that passkey and move on.
That’s how I use them. Passkeys on two Yubikeys. And I tag in my password manager which credentials have what form of auth. UP, TOTP (also stored on the two Yubikeys), Webauthn or passkeys (the former indicating 2FA).
None of the password managers (including but not limited to ones built-in iOS/Android) work that way. The Apple one (and I think Google is the same) keeps the private key inside the secure enclave (security processor), but it is still copied to each new device - though it is end-to-end encrypted during that transmission.