I've never just clip one biner to a bolt because, there is a issue of leverage, by this i mean if your biner is twisting or just moving around on the bolt, there would be more presure when it bangs aginst the rock, increasing the odds of your biner gate to open... with a draw, the pressure is absorbed by the runner. in aid you do clip directly to a bolt or to your gear, but that is just for the aid, I still use a draw for my safety rope... another reason would be draws allow your rope to extend further away from the wall causing less friction. this may not cause any danger to the climber but it does add to the longevity of your rope... I'm sure the guide is a great and experianced climber, and probably climb more and harder routes than I, but none the less I would not follow his exsample, especaily when guiding another climber...