Cruise Automation was very lucky to be acquired by GM before they got a similar letter. Similarly, Otto being acquired by Uber. They were both proposing to sell similar add-on systems. Their valuations would have been much lower after receiving such letters.
NHTSA has it right. "It is insufficient to assert, as you do, that 'your product does not remove any of the driver responsibilities from the task of driving'. As you are undoubtedly aware, there is a high likelihood that some drivers will use your product in a manner that exceeds its intended purpose."
Did Tesla got a similar letter? They have exactly that problem and exactly the same excuse. Tesla claims “Autopilot is an assist feature. You need to maintain control and responsibility of your vehicle.”
Here are three dashcam videos of Teslas crashing on autopilot. These are the three where there was a stopped vehicle partially blocking the left edge of the lane, and the Tesla plowed right into it. Tesla blames the driver. Looks like the NHTSA isn't buying that.
[1] https://twitter.com/comma_ai [2] https://www.youtube.com/watch?v=rJ7vqAUJdbE [3] https://www.youtube.com/watch?v=xoSNw_n1Xgk [4] https://www.youtube.com/watch?v=qQkx-4pFjus