Tesla books revenue on delivery. Makes sense that they would want to deliver as many cars as possible before EOY. They want to get the cars off the trucks and into customer hands quickly as they have little storage and owners usually do not want their cars sitting outside, in unsecured parking lots in rain and snow either.
Tesla usually focuses on domestic deliveries near EOQ. After the Quarter (or year) ends they begin the process of shipping production out of the country to export locations. In the past, missing EOQ deliveries could put you out another couple of months for a replacement vehicle.
As Germany ramps up, perhaps this strategy will be revisited and deliveries world wide smooth out.
Texas production will take some of the pressure off everything coming from Fremont, but currently Tesla needs to get all their Fremont production delivered in a EOY rush.
Tesla has also mentioned that they simply cannot find enough transportation trains and carriers to handle these EOY and EOQ rushes. They hope to smooth out deliveries throughout the year into a smoother and consistant flow.
When lots of customers begin to manipulate their delivery dates at the last minute, that has got to make things difficult for the company.