I have nearly zip to go on, but I shall theorize....
the existence of THREE Obsidian Boards? Obsidian 1, Obsidian XT (the separate sale DIYer), and Obsidian 2 (the new board coming factory equipped in sabers).
Entirely speculation there, but it just makes sense to me that the new boards coming built in from the shop wouldn't need that extra cable on the USB that the DIY XT's have. Other than that, the XT and theoretical 2 could and likely would be the same since 1 didn't have FoC. *shrug* Hurray for theoretics?