No, no, no to both JCG and Consultant. The "double cut" or "tandem relay" as we run it is NOT about another cut. It is a safety play.
Ball hit into a gap for a "sure double" we have a fielder go out with a "trailer". The trailer is there because quite often, at the high school level. the OF will overthrow the lead cut. So you have a trailer to get the bad throw (high or low), otherwise a throw over the lead cut will clearly allow the hitter to get to 3B. The whole thread has been about this (I realize you didn't go back and read all of it though, so no big deal) and I assume most everyone runs "tandem relays/double cuts".....if the throw to the lead cut is good, the trailer just stays out of the way (though we also have them be the "eyes" for the lead cut verbally), and the lead cut makes the cut and throws to wherever he needs to; maybe to 2B, maybe to 3B, maybe to Home if the there was a runner on 1B.
My whole point was in response to who goes out: In most cases the 2B or SS goes out, trailed by the other Middle Infielder.....but when we have a sure double down the LF line, it is awful tough for the 2B to get all the way over to the LF line behind the SS....so, we have the 2B run directly to 3B bag, and the 3B and SS go out as the tandem relay. 1B still comes over to act as the cut home if there might be a play there, otherwise he follows the runner in at 2B for a possible back pick.
Sorry I disagree with you consultant (or more correctly with the Mariners), but at the High School level, overthrows from an OF are at least somewhat common. And if no one is on base, I don't need my 1B coming over to 3B.....I have a fielder at 3B and I have a Pitcher and Catcher who would be in that area. I also have RF to come in to the playing area. Might not be as high level as the Mariners, but it follows what Ron Polk always ran, and I'm pretty ok with that!