I’ve looked into it a bit since it was weird to me as well.
The gist of it is that you can’t buy the car without plates, as it is forbidden to sell cars that are not roadworthy. Tesla can’t get the plates themselves, since the transport authority is obligated to send them using Postnord. You can bang on the door, but the plate isn’t even in the building, it’s with some government contractor who will give it to Postnord. Postnord then will just sit on it since the workers won’t touch it.
Tesla could sell cars in Norway as some have pointed out, and there may be no duty to import cars as goods into Sweden, but if it works the same as in the NL, there is massive taxes to get the licence plate naturalized, and you can’t drive a Norwegian car perpetually in Sweden.