The two point stance has advantages with longer runs because you don’t have to raise the C/G as much (just like the two point stance favored for sprint runs) and it likely has vision advantages as well.
In theory, I prefer no backward movement, but, in reality, I would never change what is working, no matter what the theory might suggest. With backs, it is also typical that the arms are carried farther back than would be ideal for pure acceleration to allow for more balance for direction change. This arm carriage also influences the action of the back foot.