As a security engineer, I cannot overstate just how horrible this is. Phone numbers might not be an ideal 2nd factor for authentication, but to punish users for setting up 2FA by using the provided phone number for ad targetting is incredibly unethical.
It's also something that people should have expected. I don't understand how people have not noticed that all of the major sites that generate revenue through user profiling and advertising have been pushing hard for users to either be obligated to register using their phone, or to setup a two factor authentication using their phone when it's not necessary for registration.
The reason I say it's something people should have expected is because if people were more critical of the things asked of them, then things like this would never get off the ground. Instead, because people do not seem inclined to naturally believe that corporations might have ulterior motives, such practice has become common place and on some sites even mandatory.