I believe there has to be a Track C because there has to be a track in which Our Heroes exist but Sela does not.
I don't agree. The very nature of time travel in situations like this means that the effects can and do precede the cause. So the end result of the Ent-C's time travelling make themselves known before it actually does that thing.
Kind of like ST:FC. Picard and company were always part of the history of Earth-Vulcan first contact (you can't prove otherwise, at any rate - just like here), but we never actually see how this happens until the film.