Inconsistent pressure plate behaviour?

I built a machine to travel past a long distance as shown in one of sethblings vidoes (http://www.youtube.com/watch?v=zoaPk_dR_fQ) using pressure plates and pistons.

When I step on the plates, I travel like 5 blocks and then there is a machine lag for like 1 redstone tick until I travel another 5 blocks.
But when I let a mob use the machine, it gets pushed through without any redstone lag.

World files: http://www67.zippyshare.com/v/18189813/file.html
Coordinates to begin: -829 56 -157