for some reason I never have given much thought about all the various undead in Hyrule. Until now almost all of them were undead Hylians or humans. The Gibdos, redeads, stallchilds, stalfos, etc. and the occasional giant undead boss. Never an undead Goron, Zora, or Moblin anywhere in the games. I think the redead bokoblins are a refreshing change to the norm. This shows me that they might not all be perfect followers of Girahim, even his curses and magic affect them. Or this is a region that is just as dangerous to the bokoblins as it is to Link. They might be a third party of barbarians that are not completely under his control but attack and pillage whatever they can around the land. Much like the Bulblins of TP, they were only somewhat aligned with Zant and not completely under his control.