I, like most pilots have not experienced a rapid decompression but I have flown with a captain who has. The experience he shared was most enlightening. When it happens you literally feel like the back of the aircraft has exploded. Your tongue is swallowed by your throat in a second, your ears begin to hurt and teeth become a hundred times more sensitive. If you already have an ear infection or a bad filling, you're likely to pass out as a result of the instant pain. None of these can be simulated in a sim or be trained for. On top of that, the cockpit fills with a cold mist that freezes the skin. All of these aspects make it incredibly difficult to recognise and reach out for the oxygen mask and autopilot controls. Stressing or moving about rapidly to find/don the oxygen mask chews into the time of useful conciousness.
I also agree that the flight path and steady descent indicates an informed decision to initiate an emergency descent. Done correctly, the target altitude would have been set to FL100 as a minimum. However looking even 30cm ahead can be challenging and that has the potential to result in the pilot setting the wrong target altitude.