Pulling V.A at idle

Hi Everyone, Hope All Y'all, Your Family's, Friends, and any one else are all Well! I have a quick (I hope) question.
Had a Distributor done. Finally had a Bro come by to watch the tach and run the mat pedal. Before he stopped in, I checked the idle airs... 3.5 turns out ( a buddy "helped" do that when i went to the store)
So, when I set the timing ( Vac Advance disconnected, plugged hose) it was close to where it was supposed to be...
BUT, plugs were ugly, pig rich, ( pulled em and posted em here, different post)
Anyway, when I hooked up the VA, the idle snapped back to "life"! Sounded Way Tight, like it should! Question is : Why am I pulling Vac advance off Ported Vac?
Thanks Everyone!
Because it's not a ported vacuum inlet.