I don't think this is true...
When your body adapts to higher altitude, it produces more red blood cells which carry oxygen from your lungs to everywher else. This effect happens when your body releases erythropoietin in to the system, which occurs aprox 15 hours after altitude exposure. Being so, I would think you would need to be in this mask for 15 hours to gain any effect.
The best way to achieve physical performance (if altitude training) would be to "live high, train low". This combination offers the greatest benefits (increased VO2max). You could make your own hyperbaric chamber, but thats fuckin expensive/weird.