A one time use recovery passwords you can generate(or are compelled to) in case you lose access or are locked out seems like a better option, I believe mega.nz & live.com do that, if it is available with google, it wasn't obvious to me.

I love Google's rational of locking people out.

I have pop3/imap access to an old secondary gmail account, but whenever I try to log in by the browser, it locks me out and asks me to confirm who I am by adding a phone number.

I never associated a phone number with the account and have no plans to do so. If somebody did get the password, they would be forced to add a phone number they are in control of if they wanted to take it over.

So what was the point of that? Other than compelling thieves to enable and setup 2FA on gmail accounts on old accounts without 2FA that they've gained access to, almost certainly ensuring the owner never gets it back if they ever decide to check their legacy account again.