I like the answer, and the blog post. I would add that in terms of physics the tension in the line can not only be created by the action of the tip on line, but on the internal forces as the line moves. I'd just remind people who may have an overly simplistic idea of tension they got from solving all those pulley and sliding block problems from freshman physics that the tension in a line is not uniform along its length when the line is accelerating, and itself has mass. I think that confusion may have some part in the ongoing "debate".
If one part of the line is accelerating or decelerating in a curvilinear manner relative to another part there will be tension in the line due to the forces of those parts on each other. So if the rod is unloaded for a moment it only means that the force (and hence the tension) on that end of the line momentarily vanishes, not that the tension vanishes throughout the line - in other words the line is not just falling at that point in time. Depending on your point of view I realize that this may be either a useful way to understand the issue, or totally obvious and/or trivial. Annoyingly incomprehensible is a third possibility.
So for a cast like a switch cast, and to a lesser degree a single Spey there is a point where most of the line is already shaped by prior forces, and is (mostly) falling and therefore mostly NOT under tension throughout ts length. For a skagit style cast things may be different, and I think someone very experienced such as Ed might be able to intuit this tension, even though it doest exist for a moment right at the end of the head attached to the rod. After all, the caster sees the result of what is going on, and how he can effect things, and as done many tens of thousand of casts. If I see my dog catch a frisbee I can very well intuit the force of it jaws snapping shut on the disk, despite the fact I don't feel it myself.
So, and I'm not saying I'm %100 sure of the answer, I would guess if you plotted the tension along the whole line, and not just the tension at the tip of the rod, you would tend to see skagit casts have a higher degree of tension right up until the power stroke because the of greater amount of differential acceleration between the line's parts, while for many other casts, including touch and go casts, the tension (and the acceleration that is the source of it) largely vanishes THOUGHOUT the line some time before the power stroke.
Now I have said this before in less precise terms, so I apologize for saying it again, but especially for playing the physicist card.