Epitaph One was Joss's way of wrapping things up, because everyone knew they were cancelled after S1. Fox didn't even bother airing it, because of some mumbo-jumbo about how the re-filmed pilot counted as the 13th episode and they didn't need another one (apparently it was somehow made dirt cheap). Then the show got S2, and they had to figure out how to get to Epitaph One's world. Some elements of that worked better than others, I thought. But it's kind of unavoidable to have it on the S1 DVD, and that's where it fits in to the narrative on a meta sort of level. It never aired in the US, so Fox went straight into Epitaph Two from the end of S2 and there was quite a bit of WTF.