Please report AI assets that are not described as such. It is against the rules of Itch and grounds for refunds.
Your analogy is a false strawman. Counterfeit goods are forbidden. AI made things are not. Counterfeit goods are posing as specific goods. AI asset developers are not impersonating a specific artist. Now with paintings such things were done, as people tried to present fake paintings as newly found works of a known artist.
Now, if you were to find an AI asset description that specifically states it is purely handmade from sratch, that might be a different story. But how much "handmade" a thing created digitally and with help of powerfull graphical assistants can be called, is a different discussion. With digital and non digital art there is a discussion about "referencing" and "tracing". In other words, the real aritsts also copy from each other and imitate styles or outright trace images. Handmade is not a guarantee for any ethical creation process. And neither is AI-made a guarantee for "unethical" process. How do you know the learning material was obtained unethical, even by your own standards? There are voice AIs were they paid a voice actor to create such a thing. What it boils down to is that some manual work is taken over by humans that use yet again more advanced tools to do similar work.
What did portrait painters think of photographers? Their work (create an image of a person) done in mere minutes. It fills the same nieche, but looks different. Similar as to most AI looks AI and is avoided because of that.