Dunno why the downvotes, if you're willing to trust Apple or Google this is a good method for passkey usage. because your touchID/faceid/opticalid auth gate the keyring's on either of these vendors your passkey works without having to migrate them. EDIT: Also ANY device that you add to your iCloud has access to the passkeys you've made... it's a dream for secure access.
The downvotes are because the commenter did not read or at least did not fully comprehend the meaning of the post they were responding to.
What happens when the user decides to move to an Android device, or even is suspended from Apple for a suspected breach of the terms of service, or Apple decides to not support their country anymore? There are countless reasons to prefer to manage one's own access.