Steam doesn't do anything to stop devs explaining how and what they used in the disclosure. If it's "content-aware fill was used in the creation of skyboxes", they can say that

But also, I think that the issue could be solved well enough by Steam just listing what counts. If it's a grey area and a line is to be drawn somewhere, so be it. Something like CAF potentially falling on the wrong side of it is nowhere near enough of a cost to justify just not informing buyers in my opinion