I feel like you could also just report them for art theft at the very least, even if you can't prove it's AI...

I remember seeing their art in an older (but still recent) thread, that they had posted for "draw the dragon above you," and it was WILDLY different than that bio art they're claiming as theirs. It looked like the work of a very new/inexperienced artist (no hate! just an observation) and the art in the dragon bio is beyond that skill level, speaking as an artist myself tbh.