According to a trustworthy VW source from Germany but without solid part number verification: the 7.5 tail-pipes are the only item that is borrowed from the Clubsport but not the muffler. He says that "the muffler on the 7.5GTI is the cheaper 'wrapped steel' (as in 7GTI) instead of the 'stamped shell' stainless construction that is only used on the CS, CSS, R and S3"
Having a look at your undercarriage vid, it seems that the above statement might be true since my CS muffler reads:
5Q0 118 T TN6
but in the 7.5GTI the code (as much as I can decipher at least) looks like: 5Q0 (or 6) 120 DX.