Rabid Robert If you are stating the rotor phase doesn't change in relationship to the cap during mechanical advance, youd be wrong.

Further there are 2'Two' different movements going on to advance the timing at the distributer.

The first is the mechanical advance it rotates the rotor and trigger/points cam forward to cause the spark sooner. This distance is about 3/16s of a inch. Since the rotors tip is a 1/4 inch all is good.

Two now the vacuum advance, the rotor cant turn anymore as you stated, the vacuum can now rotates the pickup/points base towards the can further increasing timing Without further rotating the rotor. That's how you get get the combined amount advance degrees without rotating the rotor to far out of reach of the Caps pickup terminal. That's about a 1/4 of inch in with also.

I think you need to put that distributer back in the vise and do some more studying.

Oh, and some refunds are going to be due.

Or Maybe Im having a Hellen Keller moment, but I don't think so.