Were the torque specs for the stem and seat post clamp determined by the stem and seat post clamp manufacturers, or by the handlebar, fork, and seat post manufacturers?

It seems pretty pointless to torque up a joint based on a specification arrived at by designing only half of the joint.

Or, to put it another way, if you have a joint -- such as the stem-to-steerer joint -- where the company that makes one half of the joint (the steerer) hasn't talked at all with the company that made the other half (the stem), then both parts ought to be made with a large enough margin of safety to accomodate a wide range of tightnesses. This is the difference between bikes and aircraft, automobiles, or many other applications where torque wrenches are commonly used.