I have tried in 4.20 and 4.21 with forward rendering and in both instances I wasnt able to see Temporal AA in the packaged game, but inside the editor it was perfect. I have tried many settings convinations in the SceneCaptureComponen2D but nothing has worked, even activating the TAA by console commands.
I am doing a VR project and I have a blueprint to alternate between different spectator screens, in “SingleEyeCroppedToFit” you can clearly see there is TAA, but if I switch to “Texture” (assigned to a SceneCaptureComponent2D attached to the camera) I get the exact same view but without TAA.
As I mentioned you can actually see the TAA in the editor, but once the project is packaged then the TAA is gone.