But, for now, this action is entirely on Epic. Epic broke the rules, Apple (and the court, for that matter) said that they would continue to sign and publish Epic's Fortnite updates if they brought Fortnite back in line with their contract, and Epic not only refused to do so, they submitted more Fortnite updates that broke the rules, before eventually entirely removing Apple's IAP from the iOS version of Fortnite (just before Epic's developer account was banned).
One other thing to consider: even if the IAP rules are invalid, Apple still can decide who it wants to do business with (unless the court rules iOS an essential facility, which basically invalidates the entire closed ecosystem business model, which would really up-end the tech world).
Epic willfully not coming back into compliance with their contract is entirely on them, and lends more credence to actions Apple take against them.
I used the phrase "can be argued" because I think the idea has enough merit to warrant being tested in court. These companies certainly have enough money and market influence to justify exploring it.
(What's really amazing is the arguments I see -- presumably from either very young or very ill-informed people -- that this is "just like" Microsoft in the 90s.)
Those marketplaces were a monopoly, and opening up competition helped the consumer.
Now apple is an oligopoly, and opening up competition will help the consumer.
https://steamcommunity.com/groups/steamworks/announcements/d...