Another thing with M mode with auto ISO is using EC. EC will not put more light on the sensor, as you’ve already chosen your shutter speed and aperture. Light on the sensor is already set.
BUT
If my zebras give me an indication that it’s safe to apply 1 stop of plus EV then I will, especially in ultra low light. That can literally mean reducing my auto ISO from 12,800 to 6400.
For my particular camera, according to photons to photos, that reduction from ISO 12800 to 6400 gives me 1.4 extra stops of DR to play with in post if needed.
Does this trump using base ISO? Not from an optimum raw expsosure point of view no. IF that is your primary objective. Does it mean I can continue using live view without looking at a black EVF? Yes ! Does it mean I can use a “set and forget” mode whilst understanding the trades offs? Yes!
So, M mode with Auto ISO and EC can be a reliable and fast way of shooting. It always comes down to priorities.