I feel sure you meant to say retarded bombs not free fall for your low level scenario.
Also, I think the OP was asking a subtly different question. I haven’t seen the video he alluded to but from the wording I think he is asking if bombs were used in a way such that the blast effects of each weapon could be combined concurrently for extra effect.
Historically (I am certainly not about to discuss any current weapons or tactics) the blast and frag of multiple weapons were just used in the conventional sense. Drop as many as you needed to be sure of destroying the target.
Weapons technology has of course moved on since dumb 500/1000 pounders. I’m sure google can be used for further amplification.
BV