I saw this on a customer's 2007 and was not thrilled with it.
The harness bar design I doubt is strong enough and what is GM thinking calling their sports seats ?

As we have on C5 sports seat the backrest has a hole that allows 5 point belts to properly fix through backrest

Customer had some shop cut notches in and sew around them.
Not sure if that wiill come apart later on and what it would be like when they use normal 3 inch wide belts over the 2 inch installed now