So they could be running short on the tan performance leather, 21" silver wheels, having problems ramping the armoring or they're batching the production runs on the seats (so they're doing a run of black, then grey, then tan, etc.).
I think the most likely scenario is a shortage of wheels or they're batching the seat production and that moved some cars with other interior colors ahead of you. My bet is the seats. And if so, this is the type of thing that shows up during low volume production but won't be an issue once volume ramps.
One more possibility: until they get enough people trained, they may have a pretty severe limit on how many cars they can deliver in one area a day.
from the Tesla Jobs site:
Delivery Experience Specialist US-CA-Newport Beach-Service 1 Full time
Delivery Experience Specialist US-WA-Seattle-Service 1 Full time
Delivery Experience Specialist US-TX-Austin-Service 1 Full time
Delivery Experience Specialist US-OH-Columbus-Service 1 Full time
Delivery Experience Specialist US-DC-Washington DC-K Street-Store 1 Full time
Delivery Experience Specialist US-CA-Los Angeles-Santa Monica-Store 1 Full time
Delivery Experience Specialist US-TX-Dallas-North Park-Store 1 Full time
Delivery Experience Specialist US-NC-Raleigh-Service 1 Full time
Delivery Experience Specialist US-PA-Philadelphia-King of Prussia-Store 1 Full time
Delivery Experience Specialist US-GA-Atlanta-Lenox-Store 1 Full time
Delivery Experience Specialist US-IL-Oak Brook-Oakbrook-Service 1 Full time
Delivery Experience Specialist US-MO-St. Louis-Service 1 Full time
Delivery Experience Specialist US-NY-White Plains-Westchester Ave-Store 1 Full time
Delivery Experience Specialist US-FL-Dania Beach-Tigertail Blvd-Service 1 Full time