If you take the rubber plug out it does the same thing except its a bigger hole located in a spot more prone to leaking if you put the bender up for storage, also the rubber plug is sometimes on the bottom of the jack so that won't really work.. My bender is at my buddies house right now so it'll be a bit before i can get you a pic..
The outer part of the cylinder is just a fluid reservoir (i know- thanks captain obvious) so opening it up to air will allow fluid to travel a little faster when you're pushing the shaft back in (lol) or pulling it out to where you want to start bending..
without being able to get you a pic the best i can describe it is drill the smallest hole you can under the swag logo on the bracket in your first pic...