I doubt it's unthinking. Valve hews pretty Libertarian, historically they've been very reluctant to ban even egregious games. If they're disallowing something it's probably because they don't feel they have any other option (presumably because they feel they'll expose themselves to legal liability and jeopardize quality of the platform).
My guess would be that they can't verify what AI you used, at least without investing the kind of resources required to actually make case by case decisions.
I'm not saying this is your position, this is somewhat tangential, but I am confused why I seem to hear from people that both AI is a force of nature and companies stand in it's way at their peril, but also that it's a delicate flower and that any kind of management may strangle it in the crib. To be clear I know you aren't making both claims, I don't want to put words in your mouth, but it does feel like it's coming from the same general community of people. And I'm perplexed by that.
But yeah, I would also be interested to play and perhaps developing games like that. If someone is developing a game like that and they wants to hire a backend dev with experience integrating with models in a realtime context, shoot me an email. (I'm half kidding, I don't expect someone like that to happen to be in this particular thread, but only half.)