Wondering what the legitimate use for this was?
Even if your architecture is so hosed that you are screencap'ing the actual screen to get an image to ship over a network connection … multiple people thought that tradeoff with security was worth it?
No, but you do need the ability to render in the background, and apps aren't allowed to do any GPU-based rendering in the background (you can't touch an OpenGL context, and while I haven't actually confirmed this I assume you can't touch a Metal one either). This entitlement probably let them skip that restriction to do fast rendering in the background.