DG, thanks, Chapter VI Alignments was very helpful.
Part of my confusion is I'm starting to read Jim Hardy's "The Plane Truth for Golfers", his theories are everyone either has a "one plane" or "two plane" swing, excerpts:
pg. 4 about Tour players: "... Ernie Els is a "pure" one planer ..."
pg. 35 about one plane arm movement on the backswing: "...as for your right or rear arm, it should be folding up and behind you ..."
The video of Ernie's swing doesn't seem to endorse this, or maybe I'm missing something?
I don't agree with Hardy that Els is a "one plane" swinger. By Hardy's own definitions, he looks a lot more like a "two planer." (At least from the pictures of Els that I've seen.)