They don't look undead at all, though. I think "corrupted Goron" basically means "evil Goron" in this case. Undead Zelda enemies are generally skeletons, skulls, or ghosts of some sort. And the fact that Ikana Canyon is the land of the dead is not really evidence that they are actually dead; I think appearance has much more priority over location.
Considering Japanese culture and how prevalent ghosts, spirits, and the like are within their superstition and mythology, I've always seen the Nejiron as these fiendish spirits that purposefully have the form of the friendly Gorons to trick passersby; similar to the Garo and how they are spirits, yet tangible all the while.
This doesnt look like undead either. It looks like Little Big Planet.
The Imp Poe was one of the oddest aspects of Twilight Princess, and half of me thought, "now they're just trying too hard," while the other half thought, "alright, I can appreciate this redesign of the common Poe," especially after I encountered the
real Poes in the Arbiter's Grounds, which I loved and think are the best designs so far. Poes have always been top tier enemies imo; I'm an avid ghost fan, and the designs of the Poes in Zelda have always intrigued me. I think the Imp Poe is a better design (imo) than the Poes from WW though: