Temporal AA and Motion Blur Does Not Work on Manually Animated Bones

Manually animated bones of skeletal meshes do not correctly work with temporal AA and motion blur even if "Per Bone Motion Blur" is enabled.

Found in 4.20 CL# 4233996 and 4.21 CL# 4234136

Unable to test in 4.19 due to project provided being created in 4.20

1. Open the attached project
2. In the world settings set the default pawn for DefaultGameMode to "BP_Tank_SM"
3. Play in editor and move the mouse around the tank
4. Stop playing in editor and change the default pawn to "BP_Tank_SKM"
5. Play in editor and move the mouse around the tank again

Results:
TAA and Motion Blur will not be applied to to the tank.

Expected:
The BP_Tank_SKM would look the the same as BP_Tank_SM