Isn't it possible that there are some arborists out there who can performs feats of daring and get away with it because they are trained, experienced (meaning practiced), and just plain talented. I mean there are people in this world who can do stuff that most of us can't do. To name a few: Navy SEALS, circus performers, professional athletes, legendary guitar players, etc. Yes it takes training and practice, lots of it, but some of these arborists HAVE done what it takes. I mean some people actually can do this shit and walk away unscathed. Not condoning, and I agree with safety protocols and follow them because I don't believe I'm that person. I'm just saying that there are some climbers out there who ARE that good. And the Brits do have a one-hand technique that they condone for special situations.
EDIT: I want to add this ... when I grew up and was working ground with my brother-in-law way down south in the pines, we had a kid my age who became our climber. He was one of those guys that was always great at any athletic endeavor. He also drank like a fish, had a bad drug habit, did a little breaking and entering, and always liked to fight. I saw this guy swim underwater across a river and come from under a log and grab a moccassin off of it once. He was known for this kind of stuff. Anyway, that was 1984. 35 years later, he is still doing tree work at very reasonable prices and has been one-handing chainsaws for 35 years without incident, and to my knowledge has never had one major accident on the job. He is considered a professional athlete in my book, and I would probably never question this guy. Point is, I just believe everyone needs to be honest with themselves about who they are and what they're capable of.