STU had the "touring car" requirement by intention of the class being for retired WC Touring Class cars..
I'm not sure what requirements World Challenge originally had for them to be in the class, but the point of the class's origin being specifically called "touring car" means the intent was there.

Frankly, I don't care one way or the other. STU is at the bottom end of the participation list right now, and there are lots of eyes looking at it. The Prod guys want us to go away so we'll quit mucking up their EP/FP races. The GT boys don't want to play with us either because we don't have slicks.. But give it another year or two at the current participation levels and many people that purpose-built cars for the class will be hoping they can fit into GT/Prod. There's no longer the 2.5 requirement, but we're averaging 1.9x cars per race.. You think they're going to give us a slot at Ruboffs with that kind of participation?
not trying to be pessimistic, just looking at the hazy side of my crystal ball....