> Apps that use a third-party or social login service (such as Facebook Login, Google Sign-In, Sign in with Twitter, Sign In with LinkedIn, Login with Amazon, or WeChat Login) to set up or authenticate the user’s primary account with the app must also offer Sign in with Apple as an equivalent option.
One could argue that Instagram logins come under social networks AND "own company login."
I'm not a lawyer, certainly, but my understanding is that exceptions trump the rules they are exceptions to. In particular I'm fairly certain that the gmail app (for example) does not allow "Sign in with Apple" even though it (obviously) offers google sign-in. I expect facebook apps to be the same, although I certainly won't be installing any to find out.
> Apps that use a third-party or social login service (such as Facebook Login, Google Sign-In, Sign in with Twitter, Sign In with LinkedIn, Login with Amazon, or WeChat Login) to set up or authenticate the user’s primary account with the app must also offer Sign in with Apple as an equivalent option.
One could argue that Instagram logins come under social networks AND "own company login."