The Pontiac's have a fully machined combustion chamber also,just like a Chrysler Hemi is, so you get a more precise and even flow in and out of the ports and chambers from cylinder to cylinder, so its more even. Plus, as you mentioned, they tailored the valve angle to maximize their agenda, even though it was different than what other GM engines were doing at the time. Most full race cylinder heads don't use angle cutters for seats any more, so the days of the angled valve seats are almost a thing of the past.
