As a (bad) hobby level artist, I'm well aware my art is probably best described as mashing together other's actual human work. But I kind of think that's true for everyone. You always see influences and borrowed concepts from other's past works in new art. If your work is posted publicly, you can't be surprised when another artist sees it and is inspired by it.
In my opinion, we already have copyright protection against AI art, it's the same you would use against anyone else. If you can show that the generated artwork is a derivative work, it's a problem and they've violated your copyright.
Crunching the numbers in your example, there's a 92% chance no coin does better than 55% correct. Randomness happens, but the law of large numbers usually refers to much larger numbers than 1000, and there aren't 1000 huge companies being investigated right now. I think suspicion is warranted here