Oddly enough, only SM Rhino's get two hatch fire points while Inquisitorial Rhino's get only one. I suspect it has something to do with the fact that the DH and WH codices are still stuck with old rules. Yet another reason why GW should update them.
Go ahead and shoot with two girls from the hatch.
It's widely accepted that two models may shoot from the firepoint on a WH Rhino, and also that the "Repair" rule is in effect.
Why?
The weapons are identically named, to the exact letter. The Rhino entry in the WH & SM codex are both plainly titled, "Rhino". They don't state, "Space Marine Rhino", or "Rhino Mark IV", or "Ford Bronco", or "Girly Tank". If the names were
at all different, then there would be compelling reason to accept the differences. A central rule to 40K is WYSIWYG rule which relies upon identical appearance and functionality for identically named weapons. Pricing and upgrades, however, are a different matter.
I don't consider it an abuse of grammar or presumptuous interpretation to use latest stats for identically named weapons. 40K is a game which maintains ongoing player/ market interest with new releases. You have to accept that the game "inflates" over time to keep interest.
I believe you will find this practice (identical function for identical name) to be in force at the majority of tournaments.
Even if you reject the compelling logic that "Identical Weapon = Identical Function", you can back the compelling logic with the following:
The WH codex does not define how many models may shoot from the fire point.
The main rule set acknowledges that it
could be more than one:
"A fire point... from which one or more passengers from inside the vehicle may fire". -64
The only place that the number of models who may shoot is defined is in the SM codex Rhino entry.
But I wouldn't go that far.
Just ask around how many GK players don't use Rending on their Assault Cannons.