Single Pattern vs Dual Pattern Camshaft

I suggest you go to the Isky Cams website, Tech Tips: is extra exh duration really necessary?
The cam companies have to have shelf grinds for the folks who think they need a dual pattern cam, so that is what you see. Many Jap & European engines have reverse pattern cams [ less exh duration ]. They are generally smaller 4/6 cyl engines & rev higher....but don't need extra exh duration to do it. Hmm.

The Willie Wanker, Thumper, Boot Legger cams have tight LSA & long exh duration to create more overlap to give the cackling exhaust sound to draw attention for those that want to be king of the kids, NOT for best power necessarily.