If I stand on the floor in a redstone-ready flatworld (or anywhere else just on a sanstone block) and do:

Then it removes the sandstone block beneath me as if Time was 0, but only client side. So when I reload the world or chunk it reappears and when I try to fall in it (what happens immediately because I'm already standing on it) the server will push me back while the client keeps trying to fall down, and the sandstone reappears when I try to place any block where it was.