You're probably correct, makes sense. I checked books and internet for reference to it but couldn't find any. Having said that, I couldn't find any reference to B-2 carrying a 1000kg weapon. Doesn't mean it didn't happen though.
Mission was written for 2.09, so it threw me when I got that message in DBW.
Bad enough being a Stuka pilot, but without a rear gunner - No Thanks.