There was only one unit that used these lids in WW2 (can't remember which one, and I don't have my reference handy), and I have not seen any pics of M36s mounted with these in WW2, only M10s. Strangely, the AFV Club kit of the M10 that comes with these lids does not provide proper markings for a vehicle from that unit...
These lids were far more widely used in Korea, so if you want to build a WW2 vehicle, I'd leave them off.
And you are right in saying they don't offer much protection, but they do stop small arms fire, which is pretty much the only thing US tank destroyers were designed to withstand. They had even less armour than a Sherman.