Issue was reported as MCPE-73698 but I noticed that this occurs in Java as well, and author of that didn't respond, so issue was closed as incomplete. Here is the issue in more details:

How to reproduce

1. Attachement 1: Four armor stands were placed in a body of water. Leftmost one does not have any boots, next one has Depth Strider I, then DS II and DS III. There is a piston under the block with a lever.
2. Lever was flipped, piston pushed all armor stands forward.

Expected result

Because Depth Strider speeds up movement of players, it should also speed up movement of armor stands, and the rightmost armor stand should be pushed a lot further than the leftmost one.

Observed result

Attachement 2: exactly opposite of expected. Leftmost armor stand travelled the most distance, and higher level of Depth Strider slow down armor stands more and more.