The poor guy is just trying to represent neck angle mathematically. Of course, guitarists are notorious for their inability to learn new tricks.
For myself, I might prefer to use an equation. I just don't trust my pencils. When I'm drawing a neck-length line, the pencil can start out with a perfect point, but how do I know the point isn't changing as I make the line? Also, how can I be sure I'm keeping the pencil perfectly steady against the straightedge? There are so many variables there, and it's all about muscle control!
I think adjustability in bridge height covers a lot of slop. Still, why not take the formulaic approach? It looks like fun.