How are you going to log in to anything using Google SSO? It's not the email address that logs you in, it's the authentication handshake from your google account. Anything using 2FA, or one time passcodes to your email address for new devices?

One example is when I lost access to an email account tied to a Digital Ocean account. It had been hosting a project VM and I never had a need to log in to it until the project shut down. I try and log in and although the credentials are right, it needs me to verify a one time code from my email address to prove I am not a bot. Couldn't do that. I never gained access back, DO required me to give them a full suite of proof of ID before I could even get them to disconnect my credit card, and even to this day it periodically restarts charges against my card and I have to contact them. Each time they escalate to engineering and engineering says they "Fixed the issue". Now times that experience by potentially dozens of accounts.