On my D750, and without feeling like an idiot, I've tried a half dozen times with the setting on and off and honestly don't know what the change does.
In both instances I have control via the front and rear dials on the body to adjust auto iso and the iso setting itself. Played with it in A and P modes.
Is there something I'm missing? Or using it incorrectly. I've got to push the iso button, then rotate dials, versus only rotate the front dial when in A mode. Is the not having to push the iso button on the body (left hand side above the 'i" button) what makes it 'easy'?
Appreciate the input.