This guy is apricot dun (ee aa Dd prlprl) but he is not light like most apricots, he literally just looks red dun. I thought maybe he's sooty, but nope. I looked up other apricot dun horses and found several others that are also apricot dun but look red like this?

What I expected from a "normal" apricot dun: link

Other culprits: (one) (two) (three) (four) (five) (six) (seven) (eight) (nine)

That first lad looks very familiar...

This is just a set of variants for Apricot, like every other coat. In the case of the first image, I actually rerolled him to look like that.
I think the idea is that, since apricot is prl on chestnut, there are some rare variants where apricot looks closer to chestnut, as if the prl isn't coming through as strong. Sort of like how "silver" horses can have varying degrees of a silvery overlay on their coat.

It's not a bug. Eve added in 2 variations to apricot as the only one we had in game was the very bright peachy toned one pictured on the second horse. There's the darker tone which is what you're talking about and a lighter tone as well now.

I definitely struggle with the red/chestnut looking apricot now as well. I've almost sold a couple of my KNN apricot mares for cheap 💔

The horse in question is the dark apricot variation. If you don't like that color, you can always reroll it.