The problem is that by acting as the sole gatekeeper for the App Store, anything that is published can be considered to carry Apple's official stamp of approval

The problem is that by acting as the sole gatekeeper for the App Store, anything that is published can be considered to carry Apple's official stamp of approval. That makes them liable for privacy violations and other legal missteps that the proprietor of a truly open platform could disclaim responsibility for. If they want to control the platform with an iron fist, they can damn well take the bad consequences along with the good ones.