The NHTSA designs tests to make accurate but gross estimation of the likelihood of injury in a collision. They manage to do so by simulating very small number of collisions, because the tests are very expensive and time-consuming to analyze. They report the results by placing vehicles in 5 categories.
In order to state with authority that one vehicle is better than any other vehicle, they would need to run a lot of tests to reach that level of comparative certainty. Like, hundreds or thousands. In order to compare vehicles that have different mass or geometry, they would have to run a number of variations on the tests.
Again, comparing the NHTSA testing to clinical trials, in order to test whether a therapy works ok, you might only need to test it in a hundred or so patients. To claim “it’s the best evar!!$#!” you would need to test it in hundreds of thousands of patients with very specific comparative controls with every other drug.
Let’s run with your winter jacket analogy. The NHTSA tests are powered to rate winter jackets into 5 categories of insulation. Tesla’s jacket was rated in the highest category, along with many other jackets. But since the test subject’s perception of heat and cold is subjective and varies from one person to the next, while Tesla’s jacket is definitely warm, the experiment is not powered to compare it directly with other jackets that receive the same rating, and extrapolate that comparison to all conditions. Tesla’s might be the best for tall people in the wind, but is not as good as others for short people in the rain. Nonetheless, Tesla claimed their jacket is the warmest ever tested. That misrepresents both the design of the experiment and the analysis of the results.
ETA:
I’m a fan of Tesla’s cars and what they’ve done to push the industry to do with EVs. That doesn’t excuse dodgy marketing claims.
