I've also had this situation when relocating countries. I had to abandon a 15 year old account (for which I also had a valid working recovery email) with a lot of issues recovering online banking etc. (Had to physically travel to another country to restore multiple services associated with the account).
I'm with fastmail now. I will never again depend on a mail service that I am not paying for.
Cellular providers have laughable security when it comes to account access and changes. The easiest way to get to someone's money and digital life is to figure out their cell phone company, and then convince them to send you a new SIM card for their account. Presto, instant to their bank account and now their google account.
This is about google wanting to tie more identifying information to a google account, and (by way of making all but "install our app" incredibly annoying) force iOS users to have a Google app on their phone so they know what IP address to associate with you at all times.
I was in the process of stripping Google out of my life and this looks like excellent motivation to speed that along.
The inherent tradeoff with information security is convenience. For a personal account, the user should decide where they want to exist on that curve. Google's assumptions that I have perpetual access to a cellular device, or a consistent ISP, are user hostile.