THX certifications imply, I imagine, that distortion will stay below a certain threshold at a given SPL, same for compression, and so on. I think the actual requirements are not public (or at least, I have not seen them anywhere) and "getting the sticker" requires to pay a fee. It matters little if they have or do not have "the sticker" as long as the technicalities are met; we´ll simply won´t know.
That said, the S7t would still be the performance monster it is with, or without the Dominus certification.