No, it's not the bow per se. The bow, any bow does nothing more than launch an arrow at a given velocity. What happens after that has nothing to do with the bow.

What determines how much penetration you get is what the arrow and/or broadhead do after they make contact with the game. If the arrow doesn't hit with all it's momentum directly behind the broadhead then penetration will suffer. An underspined arrow will likely be wagging around so a lot of the arrows kinetic energy gets wasted with a the partially sideways motion the arrow is doing.

An arrow that weighs too little (for the sake of speed) can have a lot of kinetic energy, but when contact is made the arrow may not have enough momentum to push the broadhead through. A don't forget, it doesn't take a lot of kinetic energy to shoot through deer sized game, but what kinetic energy there is has to be propelled in a straight line.

Notice I'm speaking in generalities here. I have never shot the Rage either. Not because I think it's a bad head. Having not shot it I would not be arrogant enough to say so. I don't believe in basing my opinions on what others say. I can get them for free, but I can not shot enough bow weight and 27" to even test them on game. That, and I take pride in being able to tune my equipment to shoot any fixed head I choose. I don't consider tuning a chore, but a challenge.