You're right, Tesla mistakenly believed they could cash in on calling their system Autopilot™ and somehow sidestep the connotations with the name and the damage pushing a broken implementation on consumers is causing.

The unfortunate truth is, if I gave my mom a car with the autopilot feature, she'd end up eventually trusting it and not care about the implementation details that make Tesla's system not an automated driving feature. That's scary and dangerous to market to consumers.

>Just because people mistakenly believe something doesn't make it right.

Tesla promotes it as autopilot. Words matter.

If Tesla itself selectively denies that the common understanding is the meaning they intend, then they appear to be trying to have it both ways: cashing in on the PR and cachet that the common meaning confers, while disclaiming the responsibility that goes along with owners actually believing it.

Unlike the shape of the Earth, there is no truth of the matter regarding what a word means except common usage. In certain cases a word might have a technical definition beyond the usual consensus but 'autopilot' isn't one of those words and communications to the public in, say, an advertisement have to use the common meaning of words.