The fact that there is structure to a part of the background doesn't mean there is actually something there. Look all over the place at the edge of the playable area anywhere else in the game, there is structure everywhere. Two that come to mind and have made me think are in the Phogoth strike. The first when you're crossing the little bridge inside of a large cavern, look out and you see a very detailed what looks like a foot bridge. The other is during the end of the strike, go to the edge of the platform and look right, you'll see a very detailed platform that looks interesting. My point is, it's all background. Some parts are detailed while some are not. It takes processing power to render that sort of detail so that is why they probably picked a point that people would look at such as the crack with the light coming in, to put a little more artistic effort into.