Apple makes no distinction between companies on it's platform that compete with it and those that do not, they are all treated the same, so it's hard to see an argument that this is mainly targeted at their competitors holding water.

Furthermore e.g. Apple does compete with Amazon kindle store on the Apple platform, but Google doesn't compete with AMamzon yet imposes almost identical terms on the Amamzon kindle store on Android. So if it's ok for Google to apply those terms on Android, why is it not ok for Apple to apply those terms on iOS?

This whole line of reasoning simply doesn't make a lick of sense. If it is reasonable for Apple to charge companies on their platform at all, then the evidence in the market is that their current charges are competitive and reasonable.