The Windows OS handles displaying things when an app is run in a window. Only full screen applications are supported via the Radeon settings
I honestly hope that AMD doesn't "solve" all problems like that.
I do not remember if the same situation was with nvidia card or not. But this kind of answer (Windows OS handles) can be told about everything when you launch Windows OS. But the situation here is that it's GPU what is rendering programs. It's not about monitor's herz it's about GPU load and framerate target.
Afterall thirdparty application does the job pretty well (RTSS) so why not to open new horizons for AMD? Add this feature to RADEON Settings.