That is totally arbitrary characterization and retreat paths are map dependent so your comments are rather off base.
It is not arbitrary at all.
Any flanking maneuver you do that puts you in the position where you have to retreat through an enemy strong point is a bad flanking maneuver. Not knowing the path your units will take on retreat is no excuse. Retreat paths are not random; it's simply something you need to learn and it separates the people who do good flanks from the people who do bad flanks.
No I simply think that a units with the utility of Bofors should not have the extra utility of being able to wiped out retreating squads.
The Bofors does not have a lot of utility as it is. It can not move; this is a pretty big deal.