I think passkeys were made to work in mind with complete idiots (here's a pop-up, tap it, now you have access to website without password, don't think about where it was saved or that it exists at all). I can understand parts of IPv6 like Router Advertisement being like that but there is so much customizability for the user that I can't really see them being similar that way.
To make it about security on both sides: IPv4 NAT is idiot-proof. IPv6 replaced that with a firewall that may or may not be default-deny.
Except they never considered that "complete idiots" could lose access to their phone's passkeys.
They did, that's why they sync
Right... just let me pull out my non-existent spare phone when mine breaks or gets lost.
It'll work if you have a laptop on the same account, iCloud or 1password or whatever else. If you only had a phone, you set the account up again on your new phone.
How does a person sync their passkeys between devices?