Thats interesting....Im just curious, but any chance you know the part number of the valley cover? Im looking at the Valley Cover from my LS3 Crate motor (part 12599296) and the Valley Cover from my L96 which was pulled from a wrecked 2015 2500 Silverado (part 12598833) and neither Valley Cover uses that screen...I would say it could be VVT related since the LS3 doesn't have VVT but the L96 did have VVT, maybe GM discontinued the use of the screen in the later Gen IV motors?
@Chrismnj I wouldn't worry too much about it, I have 10K+ miles on my LS3 without the screen and ran the L96 12k miles no screen and had/have 0 issues