It's not consistent at all. App Store rules are basically whatever Apple deems it to be. Why do you think Amazon, Netflix, et al can get away with some "violations" while small developers cannot?
Epic added the violating payment system to the app in an update internal to the app (not through app store review). Doing an end-run around review is what gets you terminated.
Amazon, Netflix etc submitted their payment systems to app review and got those updates rejected, which Apple is fine with.
Amazon, Netflix etc submitted their payment systems to app review and got those updates rejected, which Apple is fine with.