it's just a complexity/dimensionality issue. with 3d images, the training and diffusion principles are the same but your matrix gets one more dimension and dataset has to be of different nature. but since we don't have such datasets for training, i think these ppl somehow used the 2d trained model to create output in a dummy 3d space. i've done 3d modeling/rendering before and the challenge is just huge. this is too early but it's gonna mature so soon like everything else we've seen.

just wait for AI to publish more computer science research papers and just outdo itself, we just sit and enjoy the show. deepmind's AI already improved on matrix multiplication a few weeks ago, something humans couldn't do in 50+ years.