If you go behind a piston while it's retracting you go backwards

When you go behind a retracting piston you will go a little bit backwards for some reason best seen if you make an observer clock on a piston and go to the side opposite to the front where the piston head is. also I don't know what the affects versions is or security level or components are so they may not be accurate however I am on a Minecraft launcher on a mac.