Phone verification is 1-factor in most implementations on every popular website. It's just that the factor is now your phone, and your password can be changed with your phone number. Your password might as well not exist. The problem with phone verification is that phones are less secure than passwords. This isn't even a 1 factor vs 2 factor discussion. Again, Phone verification is 1 factor.
To be more specific, if the implementation of 2 factors requires both factors, then it is indeed more secure. If it's a form of 2 factor that requires only one factor, it's less secure, because now you have more attack surface.
To be more specific, if the implementation of 2 factors requires both factors, then it is indeed more secure. If it's a form of 2 factor that requires only one factor, it's less secure, because now you have more attack surface.