I immediately started reviewing the recovery options of my corporate account and de-linked all my personal information (personal email address, personal phone number for two-factor authentication, etc). I prefer to have my corporate account hacked for not having 2FA enabled than to risk my personal Google account to be locked. I went ahead and created a non-personal account with another email provider for the recovery options and tomorrow morning I will request my employer for a corporate phone number to set-up 2FA.
So, even though I still had access to my phone and even though I was still logged in to the gmail account, and even though I had many archived emails, I could never log in to it again and had to abandon it. Automated recovery didn't work and of course they wouldn't say why.
Having a backup seems like a trap or catch-22 when it becomes the single point of failure.
I tried everything, messaged friends at Google, nothing.
In the end the only solution that worked was waiting until a new person by random chance got allocated the same phone number, calling them, and getting them to send me my reset code they got via SMS.