From what I understand, if you board in your Y and you are a DM/PM/GM and someone doesn't show up (late connection or whatever, they will come get you and bring you up. With the % there is a DM/PM ahead of you, your chance of being called up are slim and none (as your experiences seem to show).

I may be wrong but the DM/PM/GM will get the nod always before a PO even if the PO is still in the gate area. It may also be depending on diff GA's.