I think the mace/scalpel relationship is one of role overlap.

One is a perfectly accurate skirmisher with near-riot aoe. Another is an almost-skirmisher range (enough range that it can sometimes kill domi!) perfectly accurate riot.

One has slightly more range, one has alpha, but these differences are pretty niche, the designs too close. Kinda like Blackdawn vs Brawler were before the latter became an artillery gunship called Nimbus.