The North American airlines bought it and no others did. It was not described as a safety feature -- if it was it wouldn't be permissible to make it optional.

The North American airlines bought it and no others did. It was not described as a safety feature -- if it was it wouldn't be permissible to make it optional. Even the current training does not tell pilots to know that an AoA disagree light is an emergency because it can cause the plane to enter an uncommanded nosedive via MCAS. I really don't think it's reasonable to expect the pilots to know things that Boeing is not even trying to tell them.