I have seen this gap-toothed looking tenon that you're referring to, David. I just don't get it. The only possible advantage I could see to doing that is it would make your mortises smaller. Cutting that one big long mortise is kind of a PITA, but having one long tenon in a single mortise seemed to be the strongest and most sensible option to me. I left about a half inch of empty space inside the length of the mortise to allow for expansion of the tenon, so that is a non-issue.
---Trudging the Road of Happy Destiny---