Looks like G@@gle has enforced some changes recently.
Almost two months ago, I created two throwaway accounts, and at that time, I wasn't able to avoid cell numbers, so I used temp ones.
Then, from the personal profile, I removed the cell number of one of these accounts.
Two days ago, I tried to use (log in with) these accounts, and the one with a cell number G@@gle asked me for verification. No way to bypass it. Of course, I already lost access to it.
The second one, which I managed to remove the cell number from, can't be used either. G@@gle asked me to add such to continue.