OK, I'll try to go slower...
The military does its best to eliminate decision making. They have protocols and training so that decisions are minimized. Thinking for yourself is not going to get you far in the military. The military is therefore a poor example. Any bets on what it takes for entrance into the military academies?
So what might be the reason a person is a "bad test taker"? Your assertion is that it's not a measure of their intelligence nor their ability to handle the stress of the test situation. So what is it then? Some "mystical power" that some people are not blessed with? LOL!
So what exactly does the ACT measure/expose if it's not academic preparedness nor stress tolerance? Do you have data to back up the claim that it is not an indicator of success in school or in life?
See:
While everybody loves to point out the exceptions, the data supports the validity of the ACT for college success. As to success in life, well, first success must be defined and then, well, there will be no need for more of this sentence...