They usually do a noticeably bad job at kerning and text in general. They’ve gotten much better but it still doesn’t quite match the results of actually using a font/computer-generated text.

They also tend to not lay things out in quite the pixel perfect way you’d expect from a good designer. But that’s not as good a tell because many designers also fuck this up.

I probably wouldn’t catch these good examples as AI in a casual context, but those tells would be enough to decide if I was asked.