Would you not think it is such an important item (how much useful consciousness do you have left once the masks drop?) that it merits a briefing? In Europe so many low-cost carriers are using secondary airfields with short runways and executing bleeds off take-offs to nurse a few extra pounds of thrust out of the engines, then forgetting to switch it on again, that pressurisation warnings are more common that one would like to think. I know of one incident involvng a well known airline where cabin crew thought some pax were showing the early signs of hypoxia.
What's new about Bleeds Off take offs? - we did them for years on a regular basis when I was on the B737-200 and -300.
On the a/c I am on with a loco in Europe I have yet to do a Bleeds Off take off in 2 years of operation!! That said of course we should know how to do same and reconfigure when airborne etc.
talent, I am not quite sure what point you are making - I would have thought all professional flight deck crew on jet a/c are aware of the average times of useful consciousness at 35/38,000 ft - what's the big deal?