Passkey is some sort of specific unique key to a device allowing to use a pin on a device instead of the password. But which won’t work on another device.
Now I don’t know if that key can be stolen or not, or if it’s really more secure or not, as people have really unsecure pins.
If your MFA is bound to a single device and you have no backup then you’re doing it wrong.
You can accuse companies of doing it wrong by often only providing a single additional factor, but I don’t see what that has to do with me.
What I’m hearing is that when an authenticator app is the only option, you’ll go with nothing over something.
Perfection is the enemy of good after all.