I used to agree with this premise. But with this new bow, the last three times I've "tuned" it, has been from it being almost completely disassembled, and starting from scratch. I went through the entire process to get it shooting right through paper, then bareshaft/fletched out to 40 yards. Once it was dialed in, I added broadheads to the mix. In all three efforts, no adjustment was needed to get the bow to shoot broadheads with field points out to 80 yards.
I'm pretty sure we are fudging things to get broadheads to fly with field points in most situations. And I'm pretty sure it's because of form/grip issues.
I am not positive on this, and different broadheads may mean different results. But in my experience, if you get a bow right enough to shoot bareshaft with fletched out to 40, and slap broadheads on, you should have no difference in broadhead impact out to that same distance. If you do, it isn't the bow.