A lot of (non-AI) photos of humans tend to be airbrushed by (human) photo editors -- this removes natural imperfections -- like patchy skin, acne, discolouration etc.
In AI models, I think the pictures the AI generates is biased to generate is also a form of "airbrush" except the model makes the reflectivity of the images high -- simply to hide the fact that there _arent_ any imperfections that would make the photo more realistic.
In other words, gloss is just a form of airbrushing -- AI does it to hide the fact that there are no more details available.
I would guess that AI models could make the airbrush more like the airbrush human photo editors do by changing some hyper-parameters of their models.