To the day where your device breaks, you had set a passkey to access your Google account (because the phone did prompted it up and you did not understand and clicked yes), you did not setup a recovery method (such as another email/SMS) or you did setup a recovery method that still depends on the Google passkey access (e.g. a second email account where you sign in with Google or has Google as a two factor verification!) and you are locked out of your Google account. Good luck at that point contacting Google assistance, you may as well consider that account as lost forever since there is no way to talk with an human being.

And unfortunately is something I start to see to family members/friends that are not tech experts when they ask me to setup them up a new phone... at least the passwords they would have written them in some notebook that they had at home, or always used the same for everything, but with passkey... and when you tell them that they lost access to their email, possibly the files backed up to Google Drive/Google Photos, etc they are surely not happy.

Also passkeys makes it difficult to get access to your account in an emergency scenario, what if I loose my phone and I'm not signed in to other devices? Maybe I've setup an SMS as a recovery method, but first I have to get to my phone company to request another SIM card, maybe I'm on vacation on the other side of the earth in vacation for 2 weeks, I'm locked out of my Google account, and from all accounts that uses the passkey as a sign-in method (including, for example, the account that I need to use to check in on my return flight, or my banking app that I need to pay stuff!)