there is indeed no real difference in work load, but i can see another reason for this.
on my network we use a forum where people can come complain, but most people aren't very eager to port their host online so just post the reason of the akill. in BOPM glines i avoided this by adding id's in the reason, with anope i still need the entire host though, but then again those are placed manually instead of automatically so it can't be that hard to make each reaosn unique...
anyways, serveral core functions place akills and the akill subroutines are in the core and can't be changed by a module... you could have a module modify the akill add .. reason, but that s just a workaround that would only partially work.