LTNman as a close (and probably weary!) observer identifies the pinch point:
It will just take one car to double park to drop someone off to bring the whole drop off zone to a standstill.
I am repeating myself but the decision to save money 15+ years ago and NOT put a proper through road tunnel - has bitten them at every turn. [pun intended]
When they built the new terminal, they could have constructed a cut-and-cover road tunnel first and made the whole place one-way. They would have gained flexibility and double lane capacity but, like everything else, the cheapest possible was chosen.
I sit to be corrected.