Timbbeal,
So what are you saying? If you didn't have the exact example he did, you would always snap your line exactly to the edge of a mortise/tennon? Let's say your reference face is not uniform. What do you base the measurements of the end points of your chalk line on? Do you stretch a chalk line to hit the highest points of your reference face and measure from there?
What if you have multiple mortises in a face at different locations like a beam intersecting in the middle and a brace whos mortise is not centered? Just trying to clarify and get a better understanding...I'm really surprised that there doesn't seem to be a nice layout video out there that shows all three techniques and their nuances. That would be a good thing for the guild to sell online. I've heard that there have been demos at conferences. Surprised no one taped them for a video. There could be quite a number of demos by different Timber framers.