I tried maximum performance plan too and same thing, constantly 3.6GHz until it needs to boost. Not sure if that matters too much but the fan on the cooler is incredibly loud because of this, it's constantly at 50% speed according to fancontrol but it can go higher when needed. Using an NH-U12S and it can get up to 78C seemingly randomly but generally stays below 75C when playing CPU-intensive games like Valorant or RDR2. Normally I wouldn't care, but I'm worried about longevity in this case. It can only boost up when needed like while I'm playing games.
I've tried using the balanced power plan (and manually editing it to make sure that the minimum state is 5%) to no avail.