Those are vents. Polaris offers a windshield (tall) that has those vents in it. The vents don't actually "vent" air in to cool you off - they are there to equalize the pressure behind the windshield to match the pressure in front of the windshield. This helps the wind deflect farther over the cockpit and prevents the curling effect. In a way it pulls the warm air from lower in the cockpit to up over your head (so it helps move the air a little, but not like you think).
I must disagree with you about this new Polaris windscreen since I'm an owner of it and the vents do work as I believe were designed.
Maybe because I have the Slingshade top but I do get cool air inside the cockpit when it is Hot outside and it does prevent cold air from entering when closed and the extra height keeps that cold air away from my face as well as reduces the amount of rain coming into the cockpit and striking my face, and I have been using this for well over a year now! Also, I have had no issues with fog on this windscreen at any time and I have over 18k miles with this windscreen in just over a year now.