Good instincts probably. Don't know much about it, but smells like further kyc of sorts, at least for first two options I listed (if I understand say iCloud keychains...which I kinda don't, but it's connected to appleid so that's not great)
Discussion
The one benefit I can see is maybe a way to hold 1 company accountable for all your login security
"You made this device, you told me it could handle logins securely with your backend, you handled my logins, I am writing you this letter to inform you I will be suing you in court and/or bombing you for this money I lost when I was hacked"