Variation in size of weaponries, at least in South East Asia, seemed quite common. There are little Javanese spear blades 5inches long and there are monsters 2-foot long, I've heard. Small ones could be for talismanic uses, large ones could be 'presentation' or 'ceremonial' ones, being too heavy or unwieldy to use. Or maybe it was the weapon of a particularly large warrior.
I've read about moro spears 18 inches long which were actually used, but this is the 1st time I'm seeing one.
Same thing happens in sundangs -- I've seen blades range from 18 inches to 27 inches.
Maybe there isn't much explanation to it. S.E.A. harbours lots of quirks. But that's part of cultural evolution in a region of ten thousand islands, isn't it.
