Thanks Scott! It made a noticable difference.
I struggled with the loud fan in this NUC model for a while. I upgraded BIOS a month ago to 0062, and yesterday to 0063.
Changing the settings in Cooling tab did nothing, like they were completely ignored. The fan(blower?) was running at constant 3700-3800 RPM regardless of what I did.
I think the important part when trying to solve this was to do BIOS upgrade using Recovery option (turn off, plug in usb stick with update file, hold power button for 3 sec, then F4), instead of the F7 or other option. I did Recovery with 0063 version (it was already on 0063, but previously I did it F7 way). It seems this one actually "unblocked" the Cooling settings for me.
Once it started to obey the settings I played a little with various settings, but eventually settled on the values shown in Scott's screenshot.
Note that when you're in BIOS settings the system seems to be running at full speed, with no power savings etc. So trying to observe if you have the settings right while watching the BIOS Cooling tab is not the best test.
That is correct; you definitely cannot tune this while in BIOS. When you are in BIOS Setup (Visual BIOS) or the UEFI Shell, all power management features are disabled and, because interrupts are also disabled, the processor is free running; spinning in a loop constantly polling for mouse or keyboard input. As a result, the processor is going to run much hotter than when at Windows/Linux idle state.