Well, since I've been quoted here, I might as well clarify what I said.
T14-1009 -- you are correct that with a compound radius, the changes occur over the course of the entire length. Not fret by fret, of course, but section by section, and from start to finish.
I'm not building Mithrandir a guitar. And in casually responding to his question about how I build my necks, I did not describe my fingerboards as being a compound radius because the aren't -- so his posting of my PM really isn't a response to your observation T14. Fact is, I make fingerboards with a 12" radius from start to finish. However, at the fret leveling stage, I also "ramp off" the last 6 or 7 frets so that, for example, the 17th fret is slightly higher than 19, which is slightly higher than 21, etc., etc. That allows for super low action, if that's what you're after. In the course of ramping off those frets, I also flatten them from the center out toward the A & B strings -- reducing the 12" arc -- which mimics the effects and playability of a compound radius but it is not, technically at least, a compound radius in the way that I think most people use the term.
I didn't invent the technique and while I don't really know, I assume it's a fairly common one (since both of the builders I've really watched on YouTube utilize it). I love the results, and I like owning exactly one sanding beam!