In reply to Yorkspud:
Yeah, kinda occurred to me too, that did. It is purer, in my view, to do climbs with less, you and the mountain. Having said that, it does seem a tad odd to want to do it without oz but have the latest down clothing, heated hand and foots warmers, fixed lines etc. In those extremes, a person picks what they want to do it 'without' and that is it. Doing it with oz but in a pair of speedos is much purer than fully kitted without oz. Yeah the oxygen level is lower, but the temperature is too, yet it is OK to be purely pure and protect yourself from lower temps. Why, oh why, then, are 'pure' mountaineers allowed to be called so when the guard against lower temps, or lower anything else for example.
It is actually impossible to grade it. The only, real and ultra pure ascent is to summit (and this is ridiculous, but true) with nothing. We have to keep warm, have to breath, have to drink, have to eat. So when all these factors become absolutely critical on high mountains, who has dictated that the breathing part is most important. To ascend with oz but without one of the other three factors is just as pure, in my view.