It may be that the tire kit isn't available in specific markets (like the US). I know US cars come with a honking huge group 94 battery...80 Ah rating...required for ample reserve for all the electronics and the auto idle shut-off "feature," but it takes up a great deal of space in the battery well.
If they use a smaller battery in other markets there may be sufficient clearances to allow the tire kit....there is a part number, it's just not available to U.S. dealers.
I gotta make friends with someone who owns a RLX (assuming I can find one). It may be the RLX kit physically fits, but with the big battery there might be some clearance issues that bother the department of Karens at NTHSA or Consumer Reports. I dunno, but I got a TLX and I got a borescope and I'd like to look.