I feel like the difference should be that if you are merely providing a market, then the customer must "belong to" to vendor: at bare minimum, the vendor must know who they are; Apple, however, insists that the customer belongs to them, that the vendor will learn nothing about the customer, and that the vendor is merely providing software to Apple under a license that allows Apple to sell copies of it to their customers... they absolutely should have full responsibility for the things they choose to sell in this scenario. Apple also certainly isn't just checking "does the paperwork look good": they are carefully examining the product, vetting it, and then claiming on their website and in all their marketing materials that customers can feel safe using all of the apps they sell because of this curation, for which they take a handsome cut of the profits. It is all simply ridiculous, really.