I don't think we ever publicly stated that as the reason.
at the risk of starting a flame war - what DID happen with BtRL? what happened to make you guys split?
Creative differences.
It's not something we want to reveal to the general public. By the time the split occurred the issues were already large enough that a split was inevitable. The team didn't particularly want to hear people completely unconnected to the team tell us what we should have done differently nor hear from people who would inevitably have offered to try to mediate a reconciliation (A complete waste of time by that point).
Secondly, there is no way to explain such a split without causing open hostility between the teams. If we explained our side of the story, Omni would be forced to explain his side. No one on the team had any interest in spending the first month after going live in a very public argument about the very things we were sick enough of to leave the BtRL team over. It's doubtful that either team would come up smelling of roses from any such mudslinging match, so why should we kill our professional image at birth? In addition, why would we risk splitting the fans into two groups who might then continue the battle long after we'd finished, moved on, and become completely sick of it?
We'd rather spend the time on the game.
Thirdly some of the reasons are plot related and thus would be hard to explain without giving away BtRL's plot. A move that would only lead to retaliation.
So to put it simply, we've got no reason to explain at the moment and lots of good reasons why we shouldn't.