Passkeys are a new technology and everyone - including users, service providers, and organizations - will take time to learn and adapt. In this interim period the recommended approach is to provide passkeys as an alternative to whatever is already offered. This is the approach that Google and many other service providers are taking.

That said, you are bringing up the right questions on the general topic of account recovery that everyone should be asking even without passkeys: "How would I login if I forget my password / lose access to my password manager / lose my second factor devices" and have a plan. Introduction and adoption of passkeys do not completely eliminate the need for thinking about your account recovery situation.

However, there is one special case where using passkeys is actually better for account recovery. If you create passkeys for your Google account on an Apple device with iCloud keychain, the passkeys are synched to your iCloud, so now even if you lose all your devices because your house burned down, as long as you have access to your iCloud account, you can just get all the passkeys for your Google accounts(and other websites).

Now, you may ask: 'what if I lose access to my Apple iCloud account" -> that's a fair question! Which is why I said Account Recovery concerns do not completely go away - but they can be significantly reduced with passkeys in many cases.