Not criticising the crew, as it seems they followed the Boeing drill to the letter.
As our fire service friend hints at though there are instances (and no one at the time is certain when they are) where any delay putting on your mask will result in incapacitation.
Have done the decompression chamber jigsaw (thinking everything was great) then been unable to execute the "now you can plug your oxygen back in" command (I just looked at the plug...looked at the instructor and laughed apparently. Really brings it home.
Hypoxia, narcosis etc all have a common symptom and that is "Impairs judgement and co-ordination and may create a false sense of security, cause disregard for safety and other foolish behaviour"
If you get into this state you are beyond the point of no return and all will be lost. The scary thing is you don't realise it is happening to you. So the "oxygen if required" statement has a fundamental flaw.
Our drill for any smoke odour or fumes in the cabin is....
Crew oxy masks....don 100%
Goggles...............don
Crew coms...........establish
Diversion..............consider
Most dangerous gases cannot be smelt and/or seen (carbon monoxide etc) there is no place for making gas conentration assessments which are only effectively made by caged budgies / canaries and carbon monoxide detectors (the latter would be easier to check in). My understanding is that carbon monoxide would be one of the gases given out by an engine seal failure.
If the Boeing procedure at least asked for one of the crew to don oxygen immediately it would make a lot more sense. Procedures like this, after all, should protect against the worst case gas scenario.