Maybe it is a couple of things, but just playing with this on my R5. If I am in Auto ISO and I spin the top wheel (the one surrounding the "mode" button) it takes me out of Auto. So, spinning that top wheel overrides ISO. In the EVF, you can see "Auto" is grayed out. I still have my Mfn button programmed to open a series of adjustment options. The first one is ISO. So, when I want to adjust ISO, I hit the MFn button, and spin the top dial (near the M-Fn button) to adjust my ISO. In this instance, if I have overridden Auto-ISO by spinning the top wheel, I can hit M-Fn button once and full Auto-ISO is re-engaged.

While I currently have that feature (Dial Func) assigned to the M-Fn button, it could be assigned to other buttons as well (just tested assigning it to the set button and it worked).