Your argument has some merit, however very rarely are these types of issues purely black and white.

I have shot aluminum arrows in the past and for the last 5 years or so have shot nothing but pure carbon shafts for hunting. I would be willing to bet that out of a properly tuned bow, you can not shoot well enough to measure the accuracy difference between your aluminum arrows and good quality carbons. Even using a hooter shooter, you can get carbon arrows to pattern through the same hole. That is not to say that the aluminum arrow is not more consistent from a radial spine standpoint, but that when you put a fixed blade broadhead on the front of it, regardless of what you shoot, the amount of steering the broadhead provides will null out any increase in accuracy from the more consistent spine.

Add to the fact that aluminum arrows have a tendancy to bend. Once that occurs your accuracy is out the window.

I do however think you have a valid point with respect to the expandable BHs with larger game such as elk. For most whitetails an expandable is more than up to the task, but if I were going for elk, I would want the extra measure of insurance a fixed blade head provides. Once again, the world is not black and white and I have seen some cut on contact broadheads have the point curl over and deliver poor penetration.