I don't disagree that it's arbitrary, but the person I replied to implied Apple changed the rules specifically to block Hey's app, which is not correct.
> Apple on Wednesday confirmed the existence of a program for streaming video providers that allows those platforms to bypass its standard 30 percent App Store fee when selling individual purchases, like movie downloads and TV show rentals. The program first became public earlier today when Amazon updated its Prime Video iOS and Apple TV apps to allow in-app purchases for the first time. It is not clear how long the program has existed, but there are at least two other providers, Altice One and Canal+, currently participating, Apple confirmed.
These examples are actually a good example of Apple violating its own principles. Three out of a multitude of reader apps that don't get this preferential treatment.
A segment gets free pass for lower fees because it is too big to get kicked from iOS while others get shafted.
Just because they can.