Hi,
may be it sounds scary (also for me as I am rule purist) but I always thougt this clarification from Warmag 16 is very much against the spirit of Warmaster, where taking initiative in small things and benefiting out that decide about final victory. So limiting options for winning side instead of dealing with losing side is just a mistake in my opinion and the rule too quickly put on Warmag paper.
My interpretation for the situation described here was based on the rulebook rule:
"Players may occasionally feel that in the interests of playability a certain leeway is allowable when repositioning units along their line of retreat. This is considered acceptable if both players are in agreement."So I was always suggesting to let the winning side to do what they want according to the rules, as they are winning and the winning with infantry against cavalry is something demanding for award rather than punisment. Following this assumption and the rulebook rules above I was just shifting remaining retareating cavalry stands 1mm away from the stands which they were supposed to slide along, still allowing winning infantry to freely choose from the options they bravely fought for.
It is more fair and much simpler solution than forcing winning side to do the drive back. 1mm "to the side" is not to much

In extreme cases you can move 1mm the winning unit which wants to stand its ground if moving retreating stands would result in destroying them.
My two cents.