AI is extremely bad at pixel art, so i doubt this. I've tried several ai's, they just cannot grasp the concept of a pixel. All they do is make a normal picture and add cubism filter to it.
if they did use an AI, i'd certainly like to know which one.
Viewing post in Free Monsters Pixel Art Icons comments
True, if you ask Stable Diffusion or whatever for a "pixel art" image it will give you something horrible, because its mainly trained on normal images. However it's fairly easy these days to customise AI models. Check this out for example https://civitai.com/models/380187/faithful-32px-seamless-blocks - this website hosts lots of AI models fine-tuned by the community for particular styles/image types. It wouldn't be hard to make one of these for 32x32 characters, you just need to get a fairly large dataset of them (unfortunately probably without having the proper rights to use them).
(the AI's output is actually still 512x512 or whatever so you get pixels of different sizes and stuff - as you can see in the preview for this asset - but it's easy to fix, you just scale back down to 32x32)