The gate picture has the same problem as as the cat one that he didn't filter out. There's a lot going on, and the lighting does seem to be one of the somewhat-inconsistent issues IMO, but it's just generally weird about why there's cats of all different sizes, why some of the smallest cats have the same coloring as the biggest ones, but some don't, what's going on with the arms of the two darker cats on the right, why aren't the sides of the throne symmetric, etc.

Everything is consistent in terms of "the immediate pixels surrounding it" but the picture as a whole is just "throw a LOT at the wall."

It passes the "looks cool" test but fails the "how likely would a human be to paint that particular composition" test.

The cat picture really shows the "noisy detail" problem with AI art. There's a lot going on on the area directly above the cat with a crown, as well as on the armrests and the upper areas of the wall background. But it's all random noise, which makes it both exhausting and distracting. A human artist would probably either make those areas less detailed, or give a more consistent pattern. Both would let those parts fade into the background, which would help draw our focus to the cats and the person.

There's other, more general issues too. The front paw on the big cat on the left is twisting unnaturally. The cat on the right with the pendant thing looks like it only has one front paw. The throne looks more like a canopy bed then a throne, with the curtains and the weird top area. The woman's face is oddly de-emphasized, despite being near the center of the piece.

Most of these things are subtle, and can be hard to articulate if you aren't looking closely. But the picture reeks of AI art, and it doesn't surprise me that the author was able to identify it as such right away.