I have a little different angle on this discussion. One of my neighbors, a diver, came to me after she recently was on a Disney cruse where she had 2 dives set up.
The first dive she allowed the DM to set up her gear. Once under water, her tank fell out of the BC strap. She tried to get the attention of her buddy, no luck. So she started to give the out of air sign to him. Once again no luck, just a blank stare from this buddy (just think if she were really out of air). So she took her BC off and adjusted the tank herself and continued the dive.
Once back on the boat she gave her dive buddy and the DM hell. After the SIT, the DM once again wanted to assemble her gear, insisting that this time he would do it right. She would have none of this; she did it herself and guess what, the tank stayed on during her dive. She has complained to the dive shop and Disney. Oh, and she insisted on changing dive buddies also. Good for her
All agencies teach how to set up your gear. Learn it, and do it. There are professionals and then there are professionals, this DM was the latter. There is no reason for anyone else to set up your equipment. You are ultimately the one responsible for your own life.