But when I opened the website, there isn't a clear warning to say "hey, this font or image pack is AI" you have to read the fine print to know for sure.

This is what annoys me on a lot of 3D asset websites as well. On steam you are supposed to declare if your game includes any AI generated assets and since there is pretty good evidence that that affects purchase numbers, I don't want to include any. Trouble is, you don't always know where everything is coming from.

Most people probably wouldn't care if some background rock was made by AI rather than the human artist, but it still technically breaking the rules, and I suspect that if someone were maliciously inclined they could really make a big thing of it.