So yesterday somehow people got ON the plane mid flight LOL.
Boarded 169 and landed with 305.

The one thing I do notice is as soon as I land the simbrief flight plan goes red and says it is no longer valid for my current flight. This is on every flight.
I have never parked at the gate and still had simbrief green.
My Simbrief plan never changes throughout the flight. It is the same generated flight and the PMDG EFB matches simbrief.
I have also not seen anywhere in the PMDG CDU to modify passengers number so I wouldn't even know how to modify it there.