I don't think that your unusual bolo is Mangyan, it's certainly Philippine and my best guess would be that it is from Luzon. The few Mangyan bolos I've seen (see the link you have provided and this one: http://www.vikingsword.com/vb/showt...ghlight=mangyan
) have had wooden handles and the tang don't went through the handle and peened at the end. This handle type I know from bolos which are attributed to Luzon, as well the tang construction. Somewhat unusual is the wooden sheath for Luzon but I've seen bolos from Luzon with wooden sheaths.