Well, as counter-intuitive as it seems I can almost believe it. One thing to consider is the even though some of the joint burns away as you smoke it, you get the extra thc that resonates on the inside of the paper when your hitting it. Unlike on a pipe, where you'd have to scrape it off when it's old and nasty. Big glass on glass bowls usually hold at least a penners worth of weed..

Also I think the measurement of "how high" you are is totally subjective. All of our minds have the ability to produce a placebo effect, so maybe we just think we're getting higher when we're hitting big ass bongs?