The factory push rod has a flat spade point that is twisted into the ground. It's purpose is to let you anchor the machine so that there is no lurching forward and back due to slop in the drive chains or to just facilitate smoother grinding. Set the anchor, release the wheel locks, and never even touch the wheel motor levers. Smoother, more accurate feed into the stump than attempting to drive forward 1" at a time. It works very well for that purpose.
Also: this machine was meant to be a towable unit also. Probably not a good idea for the open road, but it works real well for a lot of stumps. Like any other towable, back up to the stumps and use your hydraulics for incremental feed. Grind, drive quickly to the next stump. Particularly well suited for towing behind a small tractor or heavy ATV.