Well since they are planning on possibly using the lease returns on the Y (and 3) as Tesla Taxi's in the future, maybe they are fitting the SR Tesla's with dual motor and the bigger batteries (with software limitations) so that they can activate those capabilities after lease turn in for Taxi use? Since they would likely not tweak the assembly line based on leased vs purchased vehicles, they probably just push them all out with that equipment to save future retrofit costs. Tesla seems to play the long game instead of the short one.
I know our lease term for the SRY is closed ended (not allowed to purchase the vehicle after lease term is up) due to the planned use of the Tesla Taxi service and the advisor said it is due to the Taxi plan.
I would assume they would want all the Tesla Taxi's to have the long range battery and dual motor so the cars can stay in service longer between charges and also not be limited on when/where they can go (winter snow, etc.).