If you look at it from a cynical standpoint, what's happening is completely obvious. Apple is applying the full force of their developer policy -- and the pressure is mounting -- because Tumblr has absolutely zero social capital. It's a dead platform, and other than a few zealots, just about everyone's moved on.
Contrast this with Epic v. Apple: Epic has the arguable upper hand there (and Apple's flinched a few times already) because Fortnite is a massively popular game with a huge fanbase.
Contrast this with Epic v. Apple: Epic has the arguable upper hand there (and Apple's flinched a few times already) because Fortnite is a massively popular game with a huge fanbase.