two types of Piras?

[KuKulzA28]

I've been wondering about this... perhaps this has been discussed before or it's common knowledge and I'm just not educated in it. If that's the case just let me know what's what and we can be done with this thread.

Here are pictures of Piras I've found:


(they're not mine, just ones I found while surfing the web)

Do they they look similar? Yes.
But do they look like the same blade? No.

Two types of Pira?

Now I can understand that locally many varying lengths and sizes of the same blade type can be found, but Piras, Yakan's favored blade I'm told, consistently come in TWO forms... the one with the hump (which I've handled and used before) and the klewang-like one. One has a lobe at the tip's end, not unlike the Chinese Ox-tail saber or the Turkish Kilij in practice. However the other (usually larger and more sword-like) Pira has a look very similar to klewang from Sumba, Timor, etc. See below:



Now, I've heard different stories. Some folks say the Pira was down-sized and the arm guard removed to make it better for solely utility purposes. But the lobe/hump? Why two distinctly different forms of the same weapon? Some Garab/talibon were better choppers, and others had a long point for thrusting, but all can be identified by the same type of handles and blade shapes. The two different Piras look to have two different roles... sword and short-sword/machete.

So Why two?

I can see two possibilities for why the hump-back Pira was developed. Please help me out if I am incorrect here...
[1] If the hump-back Pira only began to appeared when klewang-Piras were in decline, we can see it as when the Moros were being disarmed or giving up the sword for the assault rifle. Thus what was previous a sword that was also good for hacking through vegetation became a "machete"-type blade, for bushwhacking and butchery, maybe even a side-arm for the insurgent.
[2] Perhaps they were two closely linked blades but there were and has always been two distinct types of Yakan blades - hump-back Pira for work, klewang-Pira for war. That is a possibility.

In either case, the Moros were good with blades, and they understood them well, and I am sure a specialization occurred, whether or not the two Pira types co-existed. Looking at the Mexican machete known as the Machete Costeño, one can see a possible convergent evolution of arms. Let's take a brief look at the Machete for a moment:

"[...] Angel refers to this as a "Machete Costeño". It is far from a machete, however. The Saniards discovered that the jungle was much thicker at the Oaxacan coast and the plants had much larger diameter stalks than in the interior. Their machetes with thin blades were not efficient at cutting through this growth. The Saniards modified the mariner's (or pirate's) cutlass. They shortened it and the extra weight improved matters. The modified cutlass still did not have enough cutting power so the Spanish sword makers shortened it still further and added the peculiar humback to the blade's back for about half its length. This gave the blade the right length, weight and balance to allow the Spanish to successfully hack their way to the sea from the central Oaxacan valleys. [...]" ~ Pale Horse Galleries

So... what? Am I spot on? Totally off?
Why then, are they both called Piras?
Does that suggest the hump-back evolved from the klewang?
Does that just mean a categorization error by revered academics?

Any and all suggestions, explanations, and criticisms welcome.