Generally you can't remove a login choice that easily. If you already have your own login + 3rd party logins, removing a 3rd party can create friction with your existing users.

If you only had 3rd party logins, then you can either remove them and develop a single first party login, or add Apple's login (which is likely much easier and safer). It's pretty clear to me what the incentives look like for developers these cases, and they don't seem like they could result in less choice.