I felt the same way you do until I hooked up two vacuum gauges (of similar calibration), one to manifold vac and one to ported vac. I ran hoses through the window and taped the gauges to the dash where I could see them both then went for a drive. I suggest you not take my word for it and see it with your own eyes and come to your own conclusions.
If you have a carb laying around trace the ported and manifold vacuum circuits with some compressed air or brake clean. Note the position of the ported vacuum circuit source relative to the throttle plate. Please report your findings for others to see.
