I’d be surprised if the amount of explosives was influenced by physical constraints. The aim wasn’t (and never is) to kill. It was to disrupt command and control. If even half the leadership lost hands, eyes, ears or mouths, there literally is no other option of similar effectiveness available.

But on the other hand. They needed the pagers to work for half a year or more (and still only about 3k/5k seem to have been active). Think about tech-support-but-evil trying to fix one that a boss dropped and discovering the explosives inside