Just checked on both my bodies and it only works in Auto ISO as you say. Unfortunately I have updated the firmware: the X-H2 is Version 1.11 and the X-H2S is Version 2.10.X-H2/S owners. I’ve set the Fn2 button to switch exposure compensation when in Manual Mode on/off. I’ve updated firmware and it only works in Auto ISO. Cannot remember if it worked in fixed ISO before. I’d like it to. Anyone help..?
I don't remember if it worked in fixed ISO as I never assigned a button to it. The manual only states that a command button can be assigned to switch on/off in M mode. There is no mention of Auto ISO/Fixed ISO.
Hopefully someone with a pre-latest update version will chime in.