It's not a sound way of doing things at all, but it helps Teslas short-term objectives. Delivery takes a long time to Europe and China when the cars are made in California and Nevada. By limiting the hardware variation (but not eliminating it, as you seem to believe) you can make cars and ship them before they are ordered and be reasonably sure somebody will buy cars that match, perhaps with different software configuration (a different license, really).
As you say yourself, it wouldn't make sense to sell the lower-priced versions unless you've run out of demand for the more expensive ones. Why you don't conclude like everyone else that they have indeed fulfilled the demand for the more expensive versions is unclear. I'm pretty sure they have.
What's more, they now have the problem today their cheapest model is also the best. Model 3 is especially a much better grand tourer than the S or X, it's efficiency making it go farther and charge faster.
A company improving its products so fast that they cannibalise the old ones isn't necessarily a bad thing, but it works better if you've made back the investment you made on the old product first!
I really hope Tesla makes it through the storm (I own one, so it would be something of a catastrophe for me if they don't!), but it's much more important that regulators follow through and ensure EVs are adopted ASAP. They are good for the national economy as well as the environment, at least if you're not Germany.
Turning off those features only makes sense when you can't sell at the higher price. Basically you sacrifice margins for volume. Turns out that so far they get away with not needing to do that and they definitely need the cash. So they built the 35K model 3 and then realized they could be selling it for 45K+. As long as they can sell as fast as they can build these things, why would they lower their prices?