Great explanation!

To be fair, I find there are times when using manual exposure mode is just plain easier than trying to outguess what the camera will do with settings - flash being a prime example of that. I can make it work in auto, but it's harder - and one reason to turn auto-ISO off is a mostly-dim scene with bright elements (auto-ISO will go high and so blow those out). In a more specialized situation, as a Zone System guy, I find it easier to stay in manual while I reframe rather than keep a digit on a 'hold exposure" button (might be a very special case as I'm left-eye-dominant, so my face restricts access to that button).