John,
I played and examined a Sahlin 10-string at last year's International 10-string Festival. The owner is Tom Nothnagle, from Iowa. (See his website about his cable public access TV show
here.)
This guitar was built in 1985. The only thing unusual I found about the neck was that it was made of cedar. Looked like western redcedar, but I just checked my notes, and I see that I've written down Port Orford cedar. I don't recall now where that came from. Perhaps Tom said that's what it was.
Of course, being a 10-string with its characteristic extra wide neck, perhaps it did not have this twist you're refering to. I don't recall anything out of the ordinary about its contour.
It was a very well made and nice sounding instrument. Perhaps if you wrote to Tom he could give you a bit more information about it.
Best,
Michael