From your post, it seems you think rotor phase has an effect on ignition timing. It doesn't, unless you are so far off that it can cross to the next terminal.
The timing is triggered by the pick up.
The pick up is stationary when not in vacuum advance.
The reluctor is fixed to the rotor.
Nothing in the upper half of the distributor changes without vacuum.
Timing change at the ENGINE is caused by the distributor shaft being delayed by the mechanical advance. That is all there is to it.