[whip]

I don't see how the lie angle can have a bearing on a 3d motion, if I set my clubs 6 degrees flat it would likely produce a flat backswing?

Not sure I understand the question, remember it is a general statement. the player can choose to swing on any plane angle regardless of the clubs lie angle, but he may run into problems if his/her plane is too flat or too steep beyond the lie angle of the club because they may hit the ground with the heel or toe before separation, the ideal solution as homer states would be a club a more rounded heel to toe. We have many choices in this game but the goals are the same, straight plane line, flat left wrist, club head lag pressure point, rhythm, balance and a stationary post are the imperatives and essentials of any golf motion with exception of some special shots around the greens regarding the flat left wrist.