AccessToken.CurrentAccessToken.TokenString - different results on iOS and Android

I am trying to implement Facebook login in a game. I am using PlayFab for user management. The Facebook app is still in development with only one dev user with access.

When I build the game for Android (using PC) and login with facebook via my tester profile, the login works. Interestingly the AccessToken.CurrentAccessToken.TokenString he is assigned is always the same and is the one from __https://developers.facebook.com/tools/accesstoken/__

But when I build the game for iOS (using MAC) and login with facebook using the same Facebook profile, I get a different AccessToken.CurrentAccessToken.TokenString and it fails with
/Client/LoginWithFacebook: Invalid Facebook token

What am I missing?