How does this work? Do they just hold off on building your car? or is it build then put on hold somewhere till you are ready to pick it up?
I don't think things have changed, but they might have. At least in the past Tesla didn't build the car until close to your delivery date. It costs them money to build a car, and it isn't a popular configuration, they'll have to sell it at a discount as an inventory car if you cancel. By delaying building the car they can collect a bit of interest on your deposit for a few months and if you cancel that's money for nothing for them because you lose the deposit.
Some people have delayed delivery hoping for an update between ordering and delivery and some people get lucky.