I couldn't help but think multi-shouldered tenoning has been the practice of cabinet/furniture makers for centuries.
Perhaps in the early days of timber framing--which is by nature rougher than cabinetry--(I can hear the howls now!)builders were not concerned w/ hiding their mortises or concerned w/ shrinkage issues, etc. Barns were barns and joinery in homes was often covered, etc.
Now that timber framing has been "revived" joinery is celebrated instead of hidden. I guess it seems natural that some approach the craft today more like furniture making.
So Mo's original notion that full/ multi-shouldering is done today to save time (Just cut all the tenons , the mortise is hidden, etc) may in fact be just a transition from the furniture world and a step up in quality, fit and finish.
With today's standardized timbers all planed smooth, a frame really is like a big piece of furniture. Why not create the extra shoulders? And I agree w/ Mark Davidson: a handsaw is a quick way to handle things.
