merlinextraligh, i don't think you are arguing that body steering is truly effective, and that you simply mention it as an aside, so please don't think my response below is aimed at disabusing you of that particular notion.

actually i DO have a pretty good idea of how much my body (minus handlebar input) can steer a bike...a bit, but nowhere near enough to convince me it is an effective way to turn a bike at any kind of reasonable speed and with any kind of accuracy and stability. i would never say you cannot influence the direction of a bike with ones hips, but i am positive that using countersteering and a relaxed body is really all you need to most effectively get a bike to turn.

when i worked as an instructor for Keith Code's California Superbike School, we had a "NO BS" bike which was a kawasaki 600 with an extra set of handlebars mounted and bolted only to the frame (i.e. they would not move the forks). Anyone who insisted that they could "body steer" a motorcycle effectively was given the opportunity to ride this machine. The short story is that a lot of crazy writhing and wiggling would occur, and the motorcycle would barely deviate from a straight line. We actually had one guy almost run over a portapotty and threaten to sue us because he couldn't let go of the top bars and grab the working ones until it was almost too late.

obviously a motorcycle has much more mass than a bicycle, and is not as easily influenced by these kinds of body contortions, but the principle stands that if you want to get through a turn as quickly as possible, focusing on any kind of "body steering" is not worth the investment of time and attention.