I'm not cutting Nissan that much slack. I believe they have the information, and they know exactly what orders are accepted, where they are in scheduling/production/transportation. They couldn't run a car manufacturing business otherwise.
It's clearly in their interest to keep this information private, while GM sees it as advantageous to make the information available to customers.
I don't believe Nissan (as a company) is so incompetent in the IT area that they can't possibly know where everyone's car is. They can, and they do, they just aren't giving that info to customers (or dealers). I won't speculate as to why, because I don't know at all.
Last, to those who say "STFU and wait for your car", yeah, nobody is saying information would get it here sooner.
Some people need to plan around a new car delivery. The information has real value, beyond curiosity. To them, the GM approach is superior, and Nissan's is frustrating. You aren't going to convince them that Nissan has a better system, because they don't.
Me, just curious -- I have a car to drive in the meantime and nothing material to plan.