I think there's two real issues here:

* Apple does not allow other App Stores on their platform

* Apple does not allow other payment processing or even instructions on where you can purchase things outside of their platform. This reduces even big players like Netflix to just throw up a message that says "You can only use this if you're a memeber", rather than give users a helpful link where they can purchase a membership outside the app.

Neither of these are things that Android does, so the case against Apple is significantly stronger.