Lower body half glitched in Ground by piston, while on stairs. No damage.

I built a hidden staircase in my survival game. Just to test what would happen, I stood on top of the Stairs Block as it was pulled down by the piston. When it was down, another clear stone Block would cover the hole. I did not take any damage, nor was I moved by that block, I just glitched in the ground as can be seen in this picture. I was not stuck and could jump out of the block and landed on top of it.