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
TAA and Motion Blur will not be applied to to the tank.
The BP_Tank_SKM would look the the same as BP_Tank_SM
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-62296 in the post.