They use the cheapest model to try to lure customers in and upsell them. That is why it is not available online. They don't want to sell the SR; they are likely losing money on it.
They were originally going to sell a physically different Standard Range model. Manually adjusting cloth seats, fewer speakers, a more basic center console, etc.
The update is that they won't be making a physically distinct Standard Range model, it will be physically the same as the $39k model with software limitations.
I thought they were saying they're going to stop selling the current standard one, and the new "standard" will be the software limited plus, and that it will only be available at a store and not online.
As far as I know they never delivered any of the Standard Range cars with cloth seats, and this sound like they don't plan to for the forseeable future.