"However, .. mostly I don't have to lay out the frames before cutting, which in a one-man outfit is important timesaving and back-saving. I think that is more onerous than the lengthy process of lining out, but which is also a useful selection process."

I'm not sure what you mean by the above?

I think we line out in the same way, I set the vertical first with a plumb line, the set the horizontal with the square. Alternately I will set the vertical line first with the square, then transfer that line to the other end with a level.
The last guy i worked with helped me build an octagon frame and we were setting housed braces into a 7.5in/12ft slope(sod roof) and he had a great "I get it moment" with the lines.
Something I like is just the fact that the line is in the middle of the timber, and usually very accessible to the square. I use a regular carpenter's square for layout, though I have some Japanese squares... I think I'm addicted to the number 12.
Watch out for out of square faces when working in angles other than 90, though, makes me realize why the Japanese square things up nicely.
This method is not for everybody, and not every building, IMO