Yes, like I previously said, Marantz specify 4 minutes settling time after switch on, before adjusting idling current.
We must assume that at least one Hegel engineer could blindly, reliably tell whether an amp has been on for 1 or 16 minutes 🤔🙂
Ask yourself, could you?
I have always been aware from the late 1980's when I had my first proper HiFi system that you should allow your system time to warm up, where did this come from I honestly cannot remember but as I was an avid reader of the Hifi press back then I probably picked it up from there and have carried that forward to today.
My routine when I am going to sit down and have a serious listen to music is always the same, if CD is going to be the source the system will play whilst I am doing something before I settle down, if vinyl is the source I play the first side twice.
Now have I sat and had a serious listen on a cold system, no and I have no plan to, I am just a creature of habit and will continue to be for the foreseeable.
Oh, and out of curiosity I checked the manual for Hegel's latest and greatest integrated amp, the H600 and the same message is printed in its manual, clearly Hegel believe that a warm up period is beneficial.