No-ones going to die form O2 starvation, but they might from a rushed procedure
This observation brings up an interesting point and that is the probability of several people down the back of who have been unable to get the oxy masks on for some reason. Could be a small child or someone walking down the aisle when a rapid decompression takes place. All extremely unlikely, thank goodness.
In these cases, any delay initiating an emergency descent will reduce their chances of survival or at the very least they may risk brain damage. The "book" talks about trying to get the cabin under control before making the decision to go down in a hurry. There is a good case for initiating the emergency descent while simultaneously trying to get the cabin pressure under control. Every second is critical when it comes to brain damage due to lack of oxygen and with 100 plus passengers aboard it's a good bet that at least four or five will have difficulty with oxygen masks.