Reproduced 3/3 times. Issue does not occur in //UE4/Release-4.27, so Confirmed Regression.
Actual Result: Hair is seemingly stretched and dragged back and forth due to physics velocity updating
Expected Result: Hair physics velocity should not update (compare this to an Actor Blueprint that uses the same repro steps)
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-171137 in the post.