Hey bldr...I believe you!! I absolutely believe the shoulder stopped the arrow.
Here is my good-spritied rebuttal to your theory:
1. "How about loss of energy due to over-the-top deployment of blades?"
Well, I don't disagree. An over-the-top broadhead probably wastes a little energy. But you said in this instance it penetrated an inch and a half...so this argument holds no water. The blades didn't even get into the animal. The energy loss happens when the blades are pushed open as they encounter flesh, etc. This didn't even penetrate deep enough for that to happen.
Not only that, but the amount of energy lost is so small that if that small amount of loss would have caused it not to penetrate I don't think he ever had enough to punch through with any head.
2. "How about the blades are thin and connect at one point..."
Again, doesn't sound like the blades even made it to the bone. Tip didn't get through if it only penetrated an inch, so it wasn't a blade issue. And yes, your snuffer is cut-on-contact. But you don't cut through bone...you smash through it.
I completely agree that with you about any broadhead doing the trick with a perfect shot. I also agree that you should a broadhead that is forgiving on the less than perfect shot. That's why I shoot Grim Reapers...anything less than perfect, I like a big, nasty hole. A little back, forward, low, high, etc...I'll take a big hole with lots of blood. If I miss bad enough and in just the wrong spot to square the shoulder on the joint...well, I'm not getting thru...Snuffer or Grim Reaper!!
Remember...we're friends here.
And on second thouht...let's see that picture! Ha, ha!