Mind if we re-visit this again, please?
IMHO the 'fall back' term is referring to stepping away from hacking at the enemy, and then neither standing still nor pursuing them, but rather, joining up with your standard banner and officers wherever they be calling you to come to.
The context that the rules describe, actually presents equal favor of "Fall back" being backwards or forwards (or any direction-wards) if you so choose.
With 3 basic options (pg 39) if opponent is still alive and if one side is victorious: pursue, stand, "rally in another spot that is tactically better for us lads!" aka 'Fall Back'. A better tactical spot may not be backwards. Officer may see a spot up ahead on higher ground, grabs the banner holder and drags him to the top of the hill yelling for his troops to rally on him. Could be any direction.
pg. 44 Fall Backs
" ... The opportunity to fall back gives players a chance to pull units out of combat and move them to better tactical positions."
"A fall back is basically a free move that represents the unit rallying back on its standards and officers. Unlike an evade, drive back, or retreat, it doesn't have to be made in a specific direction or over an exact distance, nor does it have to be made in a straight line." [emphasis was mine for clarity]
Thoughts?