That's not weird, it's normal. Even during periods of high demand for new cars the big automakers have hundreds of thousands of unsold cars sitting on dealership lots around the country. The only difference is the manufacturer no longer owns them, the dealers do (or their finance companies). Tesla STILL can't keep up with demand.
You point out the biggest issue with Tesla taking this approach though. For traditional OEM's, the dealerships are the ones incurring the inventory cost. For Tesla, it's themselves that have to eat the inventory cost. We know there are likely hundreds, if not thousands of Model 3 sitting in lots around the country, which means Tesla is paying to park these cars in addition to money they spent to make them. I think it would have been better if Tesla build to order, or keep very small inventory in the event that someone must have the car right away.