Oh. Then the answer appears to be that Boeing misled the FAA into thinking that MCAS didn't have the capability to cause a catastrophic failure, by understating the degree of control authority it was capable of, and therefore AoA sensor failure (and the disagree light) wasn't tied to any airworthiness issue.
I don't think a light (rather than annunciator) can be a very serious safety feature in any case, simply because in an emergency pilots aren't going to be looking at random places throughout the cockpit to see which small lights are on. They're going to be looking at the central EICAS display, which is what they're trained to do.
I don't think a light (rather than annunciator) can be a very serious safety feature in any case, simply because in an emergency pilots aren't going to be looking at random places throughout the cockpit to see which small lights are on. They're going to be looking at the central EICAS display, which is what they're trained to do.