It's entirely plausible to me that they could be training an NSFW 3D model detector, specifically because of their very minor userbase. TFA seems to presume it's all being used to train genAI, in exactly the same fashion.

We know NSFW data pollutes many otherwise non-adult datasets, so genAI is going to be trained on naughty stuff inadvertantly regardless - they might need a smut neuron specifically to turn off that sort of output.

Or they are just being irresponsible. point is, we dont know.

It's still a tad icky to scrape tons of data without asking, and downright rude to ignore robots.txt and ToS, but that's the world we live in.