Hi!
I just wrote a tool in order to fix the bad white point on my 16.2" 2021 MacBook Pro.
After checking in a shop I saw that there was noticeable inconsistency in factory calibration between units, leading to some displays being more red, more blue, or worse like mine with a depressing...
FYI finally in the iPhone 12 Pro (I think also the normal) the bug that the brightness “jumps” at 20% has been fixed, when is enabled the “reduce white point”. This bug was here since...I don’t remeber, iPhone X I think!