Those concepts may hold true for the OEM heads you mention because they were designed for one specific function, and that was the computer compatible world of everyday driving. So to say that a particular seat angle is optimum for the vast majority of engines isn't possible, because too many other variables come into play that can affect it. But in the race world, what I meant earlier about them not using multi-angle seats any longer was simply this. A standard base angle of some degree is still used to cut the seat, but instead of additional angles(hence 3 or 5 angle valve jobs)cut into the seat, they have been replaced with a multi-radius cuts instead, which greatly enhances the flow.
