Exactly... So when you put the standard reg (like a CP regulator) on at the standard pressure, there is still pressure going to that plug, which would allow you to spray windex or soapy water to see if it is leaking without the grip frame on (to isolate that it is indeed that plug that is leaking and not the solenoid or manifold.
I will put up a picture in a minute.
EDIT: Picture added.
Putting a standard reg on it makes it 1,000 times easier to isolate manifold / body plug / solenoid leaks.