Specifically the NHTSA is identifying that heavier vehicles fare better in collisions with lighter vehicles and that the test methodology relies on a fixed barrier (equivalent to a frontal impact with a similar weight vehicle). This is really the only specific complaint the agency makes and it is specifically addressed by the Tesla response.
These are the specific claims that Tesla makes about their car which did receive the best score of any vehicle of any kind tested by the NHTSA. I don’t think that any of these claims are outlandish or misleading given the outstanding results achieved by these vehicles.
