At the top of the home page I see "$7,500 Federal Tax CreditAvailable for new Model 3, Model Y and certain Model X. Reductions to tax credit likely after Dec 31." They don't say why the tax credits are likely to reduce. If I were a cynic, I'd say it could be a ploy to encourage people to buy now.
Inventory updates all the time, in real time. I had a window open to the inventory page that I'd refresh periodically. Around lunchtime I refreshed and there were no cars of interest. I took my dogs for their mid-day walk and checked on my phone (maybe 10 min after the last check) and found a bunch of new cars, including one with my desired config. I went home and bought it. It was listed for maybe 15 min.
I got a MYLR, blue, 5 seat black interior, $4120 discount. The good deals don't last long; you have to keep checking.