It's not quite a subset of Chess960 positions, because Chess324 allows different piece layouts between white and black and Chess960 does not. Edit: A comment f

It's not quite a subset of Chess960 positions, because Chess324 allows different piece layouts between white and black and Chess960 does not. Edit: A comment further down points out that only 18 of the 324 positions are symmetrical, so the vast majority of Chess324 positions could not happen in 960.