If you have B-52s loaded with just one type of dumb bombs and "Bomb Target" at just one waypoint then I think they'll drop all their loadout over the target area. They will drop it at an interval where the destruction radius of a bomb will overlap with that of the next (in F-15, at least initially, it was a fixed spacing, though I might have changed it for the patch (I'll have to check the readme to see)). They won't stay in formation during the attack though. I seem to remember trying to figure out a way to get this to happen under the right constraints for just this sort of situation so their might be a way but I'll have to think about it some more and see if I remember any more (I've got a couple of things I might give a try but it will probably be a while before I have a chance).
I think there's also a chance I might have them drop 1/2 their max load as a maximum in case they somehow got diverted (the basic part of Alt Path was set up work on any plane and could have had more than one Alt Path per mission). I think this was true for F-15 but I also think I changed it for F/A-18 to drop the whole load after reading comments on the boards. Not sure though. Easiest thing would be to either watch them or check the log to see how many were dropped vs. what is shown for that loadout in the loadout list.
Wish I could check the code and I could give you some definitive answers but hopefully this will help.