There is no benefit to tracking either forwards or backwards: It’s just where you prefer to start.
We generally recommend tracking from the point the plane you are tracking is the largest and most detailed in the scene, which may mean a combination of tracking backwards and forwards from that point.
It can also be beneficial to track from the centre of the shot if you have a very long movement, so the surface doesn’t get too small in any one direction.
Re-tracking the exact same track doesn’t improve track quality. Generally you only re-track when you are attempting to find a good placement of the search area or have added additional masks to avoid occlusions that previously threw off the track.