I don't think neck width has anything to do with it - that's a tilt-back headstock, so it's cut separately from the rest of the neck meat and glued on after the fact. Since it's glued on, there may be an adhesion issue, but they'll glue up Rosewood tilt-backs and if they aren't afraid of that, I can't imagine Canary giving them pause. In fact, the L5S in my sig has an all-Canary tilt-back. I think it may be just that Canary is a bit brittle, and cutting that particular headstock design out if it probably fails too often. I could see that pointy tip wanting to come flying off with the least amount of encouragement and turning a tough-to-get wood with a lotta kiln time in curing into a piece of useless scrap.