He was part of the MV and photobook for that album, but, he wasn't part of the comeback - this merchandise is coming from SM's already-created merchandise, not being made (not all of it) exclusively/specifically for Hot Topic (as far as I'm aware) so it probably already was printed that way prior during their main promotions.
God only knows what kind of contractual crap goes on behind the scenes too, especially if his current contracts in China exclude him from being a promotional name/making money with his name until he finishes promotions with them first (even though his parent contracting company is SMENT).
EDIT: Some of it is done specifically for Hot Topic it seems (or is out of stock and not shown on their site); some of the same merch is available through HT as well as SMGLOBAL (SHINee, SUJU, f(x), NCT etc shirts are the same on both) so who knows.
SMTOWN GLOBAL
smglobalshop.com