Imagining The Tenth Dimension

Well, we don't ignore those. If we start in the middle, we branch both forward in time and backwards. If we start at the end, we only branch backward. Those are two sound things to do as well.

You can only branch forwards. It's timelines we are talking about. Throwing a dice can get 6 outcomes, but rolling a 4, for example, only gets you one origin: throwing the dice. Keep going backwards, and you'll miss the branches coming from that throw.