Is the dealership going to take on the liability of the unit malfunctioning and crashing the car/injuring a rider? The obvious answer is no, and so you aren't going to see stuff like this on dealers' shelves anytime soon.
"Hey you should buy this aftermarket autopilot system along with the car. No it isn't sold by Toyota. It's some small company you haven't heard of. No there's no warranty. Nope no safety data. You have to accept all liability for use. Yeah it might kill you and your kids. But hey, you get to be an alpha tester!"
99% of customers are going to walk out of the dealership after hearing that pitch.
What you said would be the case if they had the baggage of "full self driving" marketing over 10 years.
What would the developers tell their partners or friends in confidence? Are their claims in confidence supported by evidence that they made efforts to validate in proportion to the magnitude of their claims? Does that differ from what they say commercially? If so, then they are communicating deceptively to further their monetary interests.
That is not to say that other manufacturers are not communicating deceptively all the time as well, but complaining about truthful statements because they do not exaggerate to the detriment of the user for the monetary benefit of the manufacturer is silly.
A good sales person would talk about any self-driving feature built in (eg lane following) then mention the car is compatible with third-party self-driving products like Comma.ai.
Just like how they talk about brakes, wheels, exhaust on sports cars - all areas customers may mod after purchase.
What's in it for the sales person or the dealership?
If a human becomes distracted for a moment and causes a wreck, that's a risk that's currently well-handled by insurance, even if it happens every 20,000 miles the person can still be insurable. If by contrast they install this, even if it does a much better job for 25,000 miles, then wrecks, if they could be personally sued for someone's 7-figure dollar medical bills + pain and suffering (not an exaggeration for sure), that's a big problem.