Following up on this for posterity...
Ordered a large. It arrived. Jubilation ensued.
However, despite the Warrior sizing guide on their own website site and Goalie Monkey's saying large is for a wingspan of 73" - 76" the backplate on the actual G5 Pro shows large as 69" - 74"
That said, I tried it on and after some adjusting, it felt great, despite the conflicting sizing information. While visually I could use another inch on each arm, I think if the arms were any longer than they are, it would rub up against the glove in a weird way, so I'm content with it as is.
Thanks to all who took the time to read and comment!