However if you compare the paint scheme of the structure behind it with a photograph of the Cougar scheme it appears that the raft structure did seperate from the aicraft because they don't match.
I cant agree with that. not based on what is visible in that photo. not even zoomed in can you see any significant detail. there is also the fact that a lot of post impact damage can occur on the way to the sea bed and from powerful underwater currents so i could not endorse your statement from the evidence you provide. if you have seen it it person, then maybe!
however, the rafts stayed on the surface so the system worked. if they remained tethered to the aircraft they would have been dragged under so you cant blame sikorsky because they floated away! a sea anchor wouldnt stop that either unless its made of iron and goes to the sea floor, and thats unlikely!