I have a 2011 LS (not the pic below) that’s plain vanilla except leather wheel, wheel controls, OnStar, and backup cam. Maybe they were throwing on leftover parts at the end of production.

Also retrofitted a factory subwoofer pulled from a wreck into a 2008 LS, which definitely did not have the needed wiring (for the speaker plus the amp)back there. Don’t know if that option had a separate harness or if cars with that option had a whole different harness.