I do not know its a bug or a hidden feature, but, the War axe can do up to 3x times the damage of the source attack. That is with or without Sweeping Edge.

Example : If you have 2 iron golems next to each other, the one being directly attacked will take less damage and the one being hit by the sweeping will die in less hits.

3x times sounds a little crazy but yea the war axe has sweeping damage by nature

Fixed with a501d5b