I’ve seen instances of lacquer peel on bumpers on other VAG forums where bumpers have been repainted and the newly painted area wasn’t prepped correctly prior to repainting, or drying process wasn’t carried out in a proper temperature and humidity controlled environment. Is it possible that your car’s bumper might have been repainted at some point during its life?
Also, over zealous use of a pressure washer could cause the lacquer to lift / peel - more likely to happen with non-factory paint or if there was existing damage (e.g. small stone chips, scuffs or scratches that‘ve penetrated through the lacquer coat). I worked with a guy who removed a large area of lacquer (almost the size of a small dinner plate) off a rear quarter panel on his wife’s Audi A3 through improper use of a pressure washer. He took the car back to the Audi dealer and they said there was evidence of repairs / repainting and there was no record of Audi having carried out the work, so they sent him on his way.