I can find rules on pg. 26 that define who the winner is, and then what that winner may do and it involves actions that happen in the assault phase. Can you point me to any pages/rules that allow you to declare a unit to be "the winning unit" at some other time or for some other reason?
Indeed you can. But winner / loser are just labeling which side gets to take actions. "The side that caused the most Wounds is the winner." Pretty simple.
"The losing unit must make a Morale and Falls Back if it fails." Emphasis on Morale and Falls Back (from
GW). There is no loser. Just the side that is falling back.
The problem here is the basic problem we have with most of the rulebook.
GW doesn't stick with terminology. The quote in question "When a unit falls back from combat, the victors....."
Now we have "victors". Since they clearly defined "winner" and what a winner was, why did they use "victor"? They didn't define 'victor". Simply because they are writing the rule in the context that was presented, which was the assault phase and they were using plain speech to describe which unit could take which action.
The rest of that line ".... attempting to cut down their fleeing foes." Shouldn't that be enemy models? Again, its flowery speech.