Manifold Vacuum Advance what am I not getting?

I just mean that you would tune the car differently for MVA versus ported that’s all. Different curve, a different total advance, a different, initial advance, etc. etc..
The difference will be at idle. For the most part once the ported signal is activated for all practical purposes manifold and ported will be pretty simular. When you say tune I assume you are refering to timing only and not air fuel ratio.