I think what he'as saying is it's better to have the right ISO than set a limit and then need to push it 3 stops in post
Well, that's not exactly what I meant; what I meant was that you will not save yourself from noise just by keeping the ISO at a limit, in M mode (it will keep noise down in Av or Tv mode, by compromising Tv or Av values). There are advantages and disadvantages to using the limit in M-autoISO.
I started out shooting birds in Tv mode, with fixed ISO. I quickly got annoyed at having to adjust ISO to control the aperture. I switched to Av mode, with fixed ISO, and got annoyed with the way that the shutter speed dropped to unusable levels if the lighting suddenly lowered, or the bird jumped into the shade. So, I started using all-manual, but still wound up with exposure problems when the lighting changes. All through this, I was dreaming of auto-ISO in M mode, as a reasonable wish (as it would seem like nothing for Canon to provide this), and as a more distant wish, the ability to make my own program modes where I make a table of ISO settings, Tv values, and Av values for a range of metered EV levels offset by the EC control.
Canon seems to either be dead from the corporate neck up, or they are intentionally holding us back to guarantee upgrade purchases in the future, as they announce their original new features that users had already thought of over a decade ago.