It's a similar story with the "recovery email address" they let you add to your account. You'd expect that if you have access to that recovery email you'd be able to gain access but no, there are cases where Google refuses to send any recovery email because "we can't verify this account belongs to you at this time" so no recovery email for you.
This would all be fine if they didn't enforce we have to have 2FA enabled and then refuse to provide support even when you're a paid up member. [1]
Now I use paid email services.
I use both Authy and Bitwarden
Its the same with your address, what if your landlord randomly decides to kick you or your house burns down? Where I live my mobile number is very secure and will not change until I fuck up very hard. And in this case I have multiple other backups (printed codes, rescue number).
Not the same at all, you can just go to the post office and file a forwarding address and all is well.
Phone numbers are very ephemeral. I have many phone numbers associted with many older accounts, like one from an office phone from a company that doesn't even exist anymore. Learning from those lessons, I go out of my way to never associate a phone number with anything anymore, it's just asking for future pain.
Literally, you are giving your account to the phone company.
I'm more convinced by the printed security codes. I have encrypted copies in several storage providers, and that includes publicly-accessible copies. I have a copy in my safe, I have some in my family's safe in a different country. No phone company involved.