They have no real hardware or store monopoly, Android still out numbers them in install base.
Legally it’s undecided at all. This is essentially complaining Walmart and Target use different means of revenue generation for placing product.
Maybe Microsoft can get a phone and store off the ground that has a bigger install base. Oh wait. Maybe app sellers should have heeded the warnings when app stores launched about this exact problem!
Just because you and others don’t feel good about it doesn’t mean it’s legitimate.
App sellers have a legitimate issue with Apple after choosing to go all in knowing how it works.