Why do they launch the passengers first? Passengers eat and shit and breathe while they wait. They're also liable to be more upset if their mission is aborted, due to a failed tanker launch, while they're in orbit.
In the Q&A part he addresses this. I think they showed passengers first for the video just for stylistic purposes. He said he thinks you'd probably be launching spaceships and begin fueling between trips (26 months), keeping them parked in orbit, and then passengers would go up last before the trip and board fully fuled ships. I think it's a detail that's not determined yet. Watch the video.
I believe his answer in the QA was that you would launch an empty rocket first, and once that rocket is fueled, a 2nd rocket with passengers would launch and transfer to the fueled rocket, and then the new passenger-empty rocket would be in orbit to be fueled for the next trip.
In the QA he clarifies that they are unsure about refueling time, it might be that they launch a vehicle, refuel it, and then launch another vehicle with passengers, then transfer those passengers to the refueled vehicle. It depends on refueling time.
If they do, I assume because it's easier to transfer fuel than passengers.