Originally Posted by
zen100
Sometimes diplomatic bags need to be observed being loaded into the hold by 2 officials, and only then do they board the plane. At the other end, they are the first to disembark, so they can observe the diplomatic bags being unloaded.
Whether that's what happened here, I cannot say. Just it's one possible explanation.
Can confirm, though usually they are the last to board and the first off, as they have to wait for the cargo hold to be closed and locked before they can go to boarding. It's possible the cargo load itself was delayed waiting on the courier bags and then that delay rolled along. I wonder if OP was able to see the bags being loaded, and if they were all loaded before boarding began.
Regards,
-Bouncer-