In my opinion, this is analogous to the cyclical universe idea, but from a more interesting, and possibly more meaningful perspective. Instead of an endless cycle of big bangs and crunches with no clear beginning, we start from a point where the universe has no measurable size, and the expansion occurs or moves in both temporal directions.
However, I'm not sure if we should view this scenario as two mirror universes, or simply as a single universe observed at two temporal points on either side of a "starting gate."
Take this a step further. Would the time dimension necessarily be a 2-sided "straight arrow" or could it instead be a circle? If it were a circle, then if you move far enough along the time dimension in either of the two directions, you would return to the origin point. That would again lead to a cyclical universe, but one in which events repeat themselves.
We already knew that gravity could theoretically lead to a closed universe where, if we traveled far enough in space, we would return to our origin point. So perhaps we could also travel far enough in either direction of time and also return to our starting point?