They are probably limiting rendering distance and degree of fidelity around assets to prop up the FPS on the XBOX. Basically rending a smaller "box" that has less degrees of detail (HD/Pixels per Millions per Asset).

There are ways to get there on the XBOX, you just don't get the same lush and dense product as you would on a PC with the same frame rate. The expectations is that XBOX users are in large to dumb to know this and focus on the carrot of FPS and don't know any better what stick was used to get to the carrot.

Don't make me have'ta Troll ya Bro!