What you have to remember is at that time West Brabant was part of Wallonia, and Luxembourg was NOT just Eastern Wallonia ~ it was the whole thing.
So, roughly speaking, for purposes of noting historic continuity of the titles of the noble families and the extant of the claim, Luxembourg included that part of the old Thuringian Kingdom that'd succeeded in breeding horses big enough to carry a mounted armored knight with weapons!
So, yeah, Luxembourg did it.
It's kind of like referring to the War of 1812 (from the American perspective) as the War between Kentucky and Canada (which, in fact, it was).