I think this is exactly the "Passkeys are a trap" argument though right? If you lock yourself into a single vendor, everything is easy and beautiful. If you choose a diverse set of vendors, it sucks so much more than passwords and password managers ever did.
On iOS devices you can import/export Passkeys between supporting password manager apps (including Apple Passwords).
In my experience, migrating between Apple Passwords and Bitwarden worked without issues, in both directions.
brother I locked myself in long before the passkey showed up
The fact that the password manager someone might use on another system is a complete piece of crap does not mean passkeys are an Apple lock-in attempt.
There are an open standard. You just have terrible software.
If that's the argument, it's bull. If you use Apple hardware, you're not locked in and required to use Apple's default Passwords manager.
Microsoft Authenticator, Bitwarden, 1Password, etc. all support storing passkeys and support multiple hardware platforms.
It's no different than making your own decision on which password manager you want to use.
Keepassxc and strongbox passkey integrations seem pretty good on all of the OSes and browsers I've used.
I think passkeys make a messy credential situation even messier, but make a tidy credential situation even tidier.