The whole battle, from the Carthaginian standpoint, is a consummate piece of art, having no superior, few equal, examples in the history of war.
Conga lines have consequences, and the fact that flanking favors the larger force cuts both ways; I see it as a way to make goblin hordes more of a threat to higher level players.
Because of this observation, it is possible that this is the action of only one figure, one of extreme athletic capabilities, which can be seen with his realistic musculature; and of high social rank, because of the elaborate hairstyle, which is adorned with ribbons and other decoration.
A flanking maneuver is not always effective, as the flanking force may itself be ambushed while maneuvering, or the main force is unable to pin the defenders in place, allowing them to turn and face the flanking attack.
The flanking force then advances to the enemy flank and attacks them at close range.
Your evaluation of the mathy bits has caused me to re-reconsider and I think that advantage is just fine.