The PreviousFrameSwitch material expression works as expected only with world position offset, but not tessellated displacement.
Found in 4.19 CL# 4033788, 4.20 CL# 4233996, 4.21 CL# 4302610
The patch with displacement does not blur properly with PreviousFrameSwitch
Both patches will be blurred
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-63178 in the post.