When I started maintaining the Atari 8bit files it was on my list to look into it, you'll notice that the same game is there in the [ATR] DATs, someone back then either converted a lot of ATR to XEX or vice versa.
I can't give you a definite answer right now, only that I'm currently looking into the [more info] flags on the Atari 8bit files, to me it looks like someone marked the "k-file" Atari *.atr files with [noATR] because they don't have a "proper" disk filesize eg 131kb or 91kb but at some point stopped using that.
The XEX files should not have the [noATR] at all, will be fixed in next release.
