That's just another mistake of Amazon nothing more and Phoronix again doesn't check facts. Amazon had these misinformation in other titles before. Look they list Tomb Raider Trilogy in the Linux games category.
Besides when you open XCOM Enemy Within page you won't see any mention of Linux in supported Platforms. Also that's an expansion I would thought that first the main game would get Linux version.
if you look at the other mentioned games there is no Linux in the platforms section. Those games landed in Linux Games category by mistake that's obvious.