While I agree with you in general, it's important to remember every car is different. And manifold vacuum at part throttle cruise, even with a healthy cam, is much higher than manifold vacuum at a cam-induced lopey idle.
I've seen perfectly street-drivable high-rise equipped cars that were built for the "look", running moderate cams and smallish carbs (2X500 CFM 4-bbls or the occasional 3X2 setup), with manual gearboxes or well-matched converters in automatics, that benefitted from a vacuum advance.