The problem here is Tesla does not make the claim that the car is autonomous, in fact they clearly state otherwise, nor it is legal for any driver to operate the car like it was autonomous
To continue your analogy Chainsaw manufacturers include clear instructions, and directions to use safety PPE.. if a operator of the chainsaw fails to follow the instructions, or where the PPE and chops their leg off the manufacturer is not liable.. Hell even if they did follow the instructions and chop their leg off it would be unlikely the manufacturer would be liable.
To continue your analogy Chainsaw manufacturers include clear instructions, and directions to use safety PPE.. if a operator of the chainsaw fails to follow the instructions, or where the PPE and chops their leg off the manufacturer is not liable.. Hell even if they did follow the instructions and chop their leg off it would be unlikely the manufacturer would be liable.