You're describing single factor, not two factor. If you can change the password with SMS alone, it's not multi-factor. I plainly stated that exception two comments ago.
Asking before you sign up, "will you allow my account to be hacked through social engineering?" isn't going to an answer other than no. Even if the answer is possibly yes.
You can check if they appear to allow it today. Not perfectly, as they may have multiple variants and depending on other factors you might get presented with one or the other.
But you have no way to predict if next month a PM there decides their current password reset was too cumbersome and they change it to SMS-only. If you had a phone# on file, you're now suddenly vulnerable.