Hmmm. Im thinking not necessarily. Manipulation or steering aside you could get to level on any plane angle Id imagine. Although as you get flatter you do approach an angle that is heel down in terms of the clubs lie angle. The vj trolio lob shot where you swing way below the hands plane requires the clubface to be opened way up to avoid the heel down problem. But you can still get to level with the left wrist. Try swinging on you knees to see what I mean.
The thing that I dont get about the endless belt analogy, is that given say Snap Release, Horizontal Hinging, Left ARm blastoff, Both Arms Straight, then a Finish Swivel and a re cocking............isnt it analogous to a small pulley wheel in Release and big pulley wheel in Finish Swivel? Maybe with a 10-3-J Pause type shot its small pulley and uncocked left wrist early and both arms straight early too, but with the left arm blasting off the chest like in a normal shot its isnt............ Dang now these guys in white lab coats are really gettin in my kitchen here. What the deuce.....