Keep in mind that the people at the tesla not-a-dealership have access to a much larger population of cars than available via the API.
Also keep in mind that if you do decide to get a "not-a-cpo" used car from tesla you'll be in for an adventure. You'll give them a large amount of money, not hear anything for a long time, then be expected to come pick up your "not new" car with relatively little notice. Then, they'll take you out to see your not-new car and you will be able to walk around, kick the tires, but not drive it. Hopefully you'll be able to put it on a charger and verify that the battery charges. Otherwise, that's it, you get what you get and you don't get upset. You can reject it, if you like; I'm not sure what happens if you do. The not-new cars are warehoused and inventoried and photographed at a
company that specializes in the "used cars nobody wants" auction circuit.
I saved $25k off of a brand-new never-farted-in tesla buying used; $25k for me is a lot of money; the 4 year not-cpo warranty is the same (theoretically) as the new car warranty, but the 2020 teslas are quite a bit better than the 2016 teslas.