I personally didn't find any insulation, but I have an RS, mayhem the reason why it is not there.
I personally just took the stock piece out and reinstalled it with the large metal washer on the bottom. Essentially, flipping each one around. Mainly because I can't be bothered to wait for it to ship across the border and visibly noticed that they can be reinstalled upside down.
Now, worst case, if I take my car in to get serviced and complain about the grind, maybe they will link it to the mis-assembly of the bushings.