I'm not sure all of the OP advice needs to be discarded. Thinking about different scenarios in advance can certainly help your mind to work well in a stressful situation. And I doubt that many of us would disagree that being ordered to lay face down on the floor or go into a back room puts us at greater risk of being eliminated as witnesses, and therefore increases the danger level quite considerably and might be a cause to use lethal force.
But since most armed robberies do not end in gunfire, there are certainly a lot of situations that do not call for lethal force and can be allowed to play out. I teach my office staff that if there is an armed robbery, they are to give the robber anything they need to give them to get them out of the building without getting someone hurt. I can replace any goods and equipment that I have, and I can go back to work and earn more money, but my staff members are real people with family and friends and loved ones, and they alone, of all the things in my office, are irreplaceable. Initiating an exchange of gunfire in close quarters at a time when there is still a reasonable chance at ending the situation more safely is not consistent with my commitment to the safety and well being of my staff, or even of strangers.