The original mockups for a Bonk RPG looked cool, but I was disappointed when I saw this in EGM.
Indeed. Hudson did a lot of mock-ups around the time of PC-Genjin 2, for new Bonk concepts, like Genjin no Tetris, RPC Genjin, Genjin no Yabou (war sim), and most of them probably were just still images created in their paint programs.
This one shown in EGM is probably the real thing, a working proto of the RPG. And it happens: sometimes real versions look a lot worse than their concept mock-ups.
On a semi-related note, on a video I have with an interview with 2 of the designers of the Momotarou series & Monbit, they said that Hudson made something like a dozen prototype concepts a month, and only a few make it through. So, it's no surprise this Genjin RPG was cancelled.