I was taught that nitrox reduces narcosis and therefore it was better to dive with a nitrox mix in the 30-40m range by my Deep instructor so yes, it was kind of sold to me as a "deep" diving gas in that regard early on as he said it would be safer as I would be less narced.
hmmm...The SSI manual states:
Until such time as researchers can verify what impact, if any, Nitrox has on narcoses, you should not count on experiencing less narcosis or impairment when diving Nitrox than you do when diving air at comparable depths.
Carrie