...But I can see how someone who isn't familiar with the "clockwise = down, counterclockwise = up" paradigm might go the wrong direction a few times before figuring it out....

To me this paradigm is wrong for the Empeg. I'd naturally try the opposite because the knob because I
m in the US and I'd be using my right hand.

I think that we are conditioned to expect things to move 'with our thumbs' when we turn a rotary knob, clockwise=down is correct if you are using your left hand, but incorrect for your right hand.

This concept appears in many other places as well, even those where physical up/down isn't being controlled. eg thermostats and volume knobs on AV gear. 'Up' always seems to be clockwise. This convention probably stems from the fact that most people are right-handed.

Ironically for a horizontal movement, handedness doesn't apply - we always put our thumb on the top of the knob regardless.

If vertical menus were to be implemented I think that the handedness of the knob would have to be selectable to cater for both UK and other drivers