I can see that LM was right when she said I should have posted this - but I'd get blown away by the ski technobabble. (as opposed to the computer technobabble which I can spew ad naseum.)
Since I've jellified my brain by spending the last 2 days setting up qmail, virtual apache servers, and tcpserver (and that's for a *hobby* not my "real job), I'm not even going to try to figure out Bob's diagrams and Bob, Todd, Gonzo and Tog's comments quite yet. But I'm definitely going to print and save them, and take a look when there aren't so many penguins running around inside my head.
As LM noted, I had casually asked her the question when browsing through Ellen's book. The images and descriptions of the converging step seemed amazingly like the concepts I learned long ago for the stem christie from Bob Beattie's "Learn to Ski" (circa 1967). I was basically self-taught from that book. Good at the time I guess - at least it took me from basic snowplow on bunny slopes up to functional though klutzy stem christies on blues and easy blacks.
Probably gave "Xena", my instructor at Whistler a couple of years ago, a lot things she had to correct in my skiing. No doubt that was the reason she had to tell me "stop pushing snow to the side of the trail, we have enough snow there already!"
I do get the "defensive" stem christie vs. "offensive" converging step in concept and feel, I think. Though I couldn't explain the biomechanics and vectors of it. I've found myself still occasionally in a bit of a stem (or "converging parallel?") on things that are a bit above my ability level but within my "ah hell I guess I can get down this ok" range. Things like the front face snow bowl at Bormio, White Heat (the groomed side - I'd die on the bumps) at Sunday River, deep powder, etc.
What I've noticed in those situations is that now though I'll still be in a "converging" position mid-turn, and in a "one-two" move, I do seem to be much more down the hill over my skis, and I'm not doing the "push snow to the side" thing as I'm doing it. It feels more like a "how I get down this steep section" turn rather than a "how I try NOT to get down this steep section" move.
Partially that's from my on-the-groomed deliberate attempt last season to stay close to the fall line, get my upper body downhill, do aggressive pole plants out forward, and do clean parallel, mostly carved turns. So I'm more used to the feeling of continuing downhill rather than earlier days of checking myself. Plus you have someone named Xena yell at you and you'd do what she wanted real soon too!
From a holistic, sensory perspective, does that seem like the difference between the stem christie and converging step? Similar moves (other than brush vs. step) but different intent and visualization of your movement?