I'm sorry, but that is NOT the answer to this puzzle.
Page 108 is just telling us what happens in P and A modes - i.e. that as it gets darker the camera will lower the shutter speed until it reaches the minimum that you have set up in the Auto ISO menu, and only then will it start to raise the ISO setting. If the ISO reaches your pre-set maximum, the shutter speed will then be reduced below the minimum.
In S and M modes, that doesn't apply.
In S, the camera will first widen the aperture, then when it reaches the lens' maximum, it will start raising the ISO. In M, the camera will (or should) start raising the ISO immediately, because it can't change the aperture or shutter speed.
Just one more thought, Dennis - I don't suppose you had the built-in flash raised or a Speedlight attached...? If so, I believe Auto ISO does not work in quite the same way.