For comparison, the falcata.xml uses 5 variant meshes, gladus.xml 6, xiphos.xml 5, and kush_nubian_mace.xml 15, and I daresay their shapes are more similar than the 5 knives in @MrLux's screenshot. Besides, those other weapons are used by only a few actors, whereas the knife is used by the slaughter attack animation of all infantry and female citizens. I don't know how much it affects performance, though I wonder whether it's significant in this case.