It's an athermic windscreen coating...
The main purpose of these is to reduce the oven effect and increased stress on air-con when driving. Why on these cars? Why now?
To cut a long story short, (involving the way pedestrians bounce from the front of bars and cD drag co-efficients) the design direction of many small-medium cars which PSA and Renault excel at is to a very raked windscreen on many models, exposing a wide area of black plastic dash to get all cooked up when parked. This effort aims to reduce the heat effects of this.
Two knock-on effects are that radar detectors are less effective mounted inside the vehicle and it can be difficult to see into the car in certain cirumstances - like a head-on speed camera. Win some, lose some. Radar detectors have a patchy legality in the EU, being entirely legal in the UK and sketchy elsewhere.