nor on my 5D III, apparently
Canon was hampered by their traditional ergonomic layout of the controls on the camera. They were defined for film, and wasn't really ready to handle the new need for exposure compensation when you also need to be able to change both time and aperture.
On the 1D-series, one could have thought that it would be a piece of cake to add, since that camera has an explicit +/- button. One could think that pressing the +/- button would allow you to adjust EC with the main dial even in M mode, just as it does in P, Tv or Av, but no. The labeling of the +/- button is actually misleading. The correct marking should be "copy whatever functionality that right now, in this moment, is present on the rear dial to the main top dial".
Clearly, this doesn't fit on the camera, so Canon selected to label the button +/-, just because it happens to be true in the cases where you haven't selected M mode, nor have set the camera to for example move the AF points or select ISO with the rear dial. If you do that, the +/- button changes meaning again.
So it took a long time for Canon to sweat out a solution to handle the EC setting when floating ISO only. Now it's there.
By the way, already the 40D had a (very) limited implementation of automatic ISO setting. It normally had the range 0f ISO 400-800, but could go down to ISO 100 if the scene otherwise was too bright.