It is not limited to the VIIB.
It also happens with the type IXB.
That makes me think it is common to all variants of the VII and IX series that retain their deck gun.
I'm so used to it now that ordering the deck gun manned and then manually loaded is the very first thing I do before leaving port.
Just remember not to set the deck gun to fire at will, or Uncle Karl will be very unhappy with you for firing on all those German ships around you.