*Puts hand to ear piece*
What's that? Good golly Miss Molly.
This just in, reports from /r/Halo and /r/XboxOne are rolling in stating that the XB1 BC Engine has recently been updated. Framerates and aliasing issues across a multitude of games are now much improved!
For more on this development, click the following link: Reddit Post with video
Good night and good luck.
EDIT: This is, apparently, just an engine update. There are overall performance gains in many games. Some are saying Reach is not yet effected, while others are saying they have seen some improvement. That said, there will supposedly be a Reach specific BC update soon.