Wired:

I spoke to a variety of developers who make apps for iOS and Android, one of whom asked to remain anonymous because they aren’t authorized to speak on behalf of their employer. Some are skeptical that Sign In with Apple will offer a solution dramatically different from what’s already available through Facebook or Google. Apple’s infamous opacity around new products means the app makers don’t have many answers yet as to how Apple’s sign in mechanism is going to impact their apps. And one app maker went as far as referring to Apple’s demand that its sign-in system be offered if any other sign-in systems are shown as “petty.”

My first thought is I wouldn’t trust any developer who would use Facebook or Google login procedures but not want to use Apple’s as well.