I do not think this is correct. Totally TKD had an article which determined a formula for increased force needed for each available piece of wood - without spacers. USed a fist cast from lead and all sorts of force gauges. I don't think the same formula applies for spacers. But everything will change radically due to needing to maintain a certain level of force over a greater distance with spacers.
Granted, the impacts are not identical. But according to one of our kids (he's got a PhD in mechanical engineering, so I don't argue with him) the difference is trivial. He points out that honeycombing makes materials stronger while also making them lighter.