I am android user, but from time to time I also recognize postings about GC.
In this german news they wrote about problems of GC related to iOS versions
If you are not able to translate the text or find a english news I try to make a 'short' of it
Depending on iOS and the games you where not able to use GC or simply have problems.
Actually GC also block some games... and iOS itself block some other things to avoid other multiplayerplatforms on iOS.
For me this sounds like a mobile multiplayer platform war/domination/monopol on iOS