The other problem RUb compensates for, as I think Beery noted, is the accuracy. The Flak gunners are super-accurate in SHIII; they'll hit the plane perfectly at 2km away when no human would really be able to.
So, RUb's consideration is both for effective range and accuracy.
I just man the guns myself if I want to shoot them from far away. At least the accuracy is human
The general result is quite alright though. Fights against aircraft seem to be pretty realistic in terms of duration, and there's been a few times when concentrated fire from late-war heavily armed U-boats brought down even Catalinas on the first pass (lucky shots I guess).
But anyway.... it's very easy to change this in CrewAI.cfg for those who don't like it.