Fair enough, although I don't see why the constant rejection and need to explain the same thing to Apple again and again seem like a normal thing to us. Their review process is too rigid and their control over your app updates is too tight, which is why they are now getting bunch of other problems with companies like Epic.
Speaking of Epic, maybe you're right and it's not just small developers.
All of my screenshots are from the second round we went through after trying to remove apple login entirely.
They bully small developers, because big companies like Uber or Grab have the same functionality with zero problems. While when we try to explain that we use phone number for the same reason, Apple insists that we change how our app looks and works.
I would not be complaining online if simply replying back would work. This is the second time we got rejected for that reason. Last time it took a week of back and forth trying to convince reviewers that we need phone number and it doesn't make sense to ask for it later somewhere.
We did get approved eventually, only to get rejected again for the same reason on the next update.
We ask phone number for the same reason as Uber does - our masters need to contact the user to be able to deliver the service. Explaining this to Apple took a week of back and forth, and only lasted for one submission.
It's not a two-factor auth, we ask phone number confirmation because our masters need to contact you to deliver our service. If there is no phone number, our app is useless for you. So it's perfectly fine for us if you want to delete the app instead of giving up your number, and it seems like a better solution for privacy concerned people.
On the other hand, if we allow to login but only request phone number later, this will seem somewhat deceiving to the user. Like we pretended that he can use the app while keeping his info private, while in the end it ends up that he cannot.