There isn't a "correct" answer here. It depends on what you're trying to do. If you are wanting to go from a ft hs to a bounder, flaring the arms (Y position) during the flight phase will shorten the body and allow the feet to undercut and then punch fwd into the bounder. To set the bounder into a flipping skill keep the arms (and body) longer to land more upright and punch up into the salto. For the salto itself, arms closer for flips and a wider set for twists (lose a little height but gain rotational speed).
We have to be flexible in how we approach skills. If I have a very tall kid, I may tell him to set his arms much wider than a shorter (or faster) tumbler. Techniques often need to be adjusted to the athlete in order to produce the best result. So, DD and DS are both correct (assuming that they were listing to their coaches correctly
). In my gym there are only two hard and fast rules: Listen and follow your coaches directions, and don't clap the chalk!