There is a significant amount of interop that already exists, that folks are looking past or just already taken for granted (which is actually fine too!). While on a Windows machine using Edge, you can save a passkey for your Google account to your 1Password vault, and use it to sign in to that Google account on Chrome on Mac (if you have signed in to the same 1Password account on the machines). Or you could use a passkey you saved to your iPhone / iCloud to sign in to the Google account on ChromeOS. This is the level of interop that exists today. This did not just happen magically - all these companies (and more) worked hard to make it happen.

Also speaking for Google accounts, passkeys are an additional option for users. Using a passkey is not preventing you from keeping any other sign in method on your account that you feel has less of the lockin risk.