All of the things in the late G line (G-6 on) were mixed in as time went on, including the Erla Haube canopy and tall rudder... and all of the other improvements. The G-14 and G-10 were just attempts to standardize this.
As such, you'll see G-6's with Erla Haubes, G-14's with short rudders, etc. etc... in fact, those two 'abnormalities' in particular are pretty commonplace. I've even seen a G-10 with a short rudder.
Our G-6 is a fairly early model, representative of a G-6 produced in late summer/fall of 1943.