Maybe Toyota does it differently from Honda but this is the way the Toyota dealership manager explained it to me: all the dealerships are grouped into a "region" such as Houston+Dallas+Austin+etc. The new cars going to those 3 cities enter the USA at the gulf port of Houston (or Galveston? can't remember exactly). If I go to a Houston dealership "A" and I want a black Camry but they don't have any on the lot, the dealer can check the entire region's inventory. If Houston dealership "B" or Austin dealership "C" has them, those other dealerships are required to swap cars with dealer "A". That way, the customer isn't forced to go to another dealer just to get a particular car. The dealers' computer screens showing inventory all show every competitors' available inventory. It's possible the Toyota manager's explanation was bs or I left out some critical details.
To make the Toyota story compatible with your Honda story, I suppose that for a dealer to sell a car, he still needs to have inventory. To sell 50 cars, he needs to be allocated 50 by Toyota Inc. But he's doesn't have to sell particular the 50 he happened to get. The "50" is really part of a shared pool of cars.