If they are required to buy them from an out-of-state location, then they are prevented from buying them in Texas. Draconian.
The statute requires that a sale of a new car in Texas must be conducted through a dealership in Texas.
Tesla doesn't have dealerships, and so is not a member of the Texas Auto Dealers cartel who lobbied for the statute decades ago to prevent having to compete with direct sales from auto makers.
So, in Texas, you go online to buy a Tesla. (sound familiar?) Yes, just like you would do anywhere. Tesla brings it to you, just like they do elsewhere.
People in Texas buy Tesla cars every day, the same way peole buy them elsewhere. There are Tesla showrooms in Texas, but you cannot transact a sale using the showroom's computer. You cannot "buy" a Tesla off the Showroom floor. The people at the Showroom are forbidden to fill out paperwork or in any way facilitate the actual sale. If it is important to you to do so, you can order a Tesla while physically at a Tesla showroom by using the browser on your phone.
As I understand this, it is not so much a matter of the physical vehicle having to leave the state and then return as it is about the "ownership" of the vehicle having to leave the state and return. It is a matter of where the paperwork is done.
As an example, lets say a company from Fremont CA manufactures something called a Cybertruck at a factory in Texas.
You buy the Cybertruck from the California company online from the comfort of your home in Texas.
The paperwork for the sale is processed in CA, then, you are provided a California Title or a Manufacture's Statement or Origin, or something to give the folks at the courthouse to register your vehicle in Texas in order to be issued Texas plates.
The manufacturer sends a transport to the factory to pick up your Cybertruck and deliver it to you. Same as they would if you had ordered an S,3,X, or Y.
Maybe you arrange to pick it up at a showroom in Texas, or have it delivered to your home, work, or other convenient location. Picking it up is not the legal sale. The legal sale of the vehicle happened in another state.
Done. Easy peasy.