variable refresh rate

AMD developer Nicholas Kazlauskas has uploaded a series of patches, that when eventually added to the Linux kernel, will enable 'FreeSync' within Linux. Adaptive sync is the Displayport spec and variable refresh rate is the same but pertains to the HDMI spec that allows for graphics adapters...

If a display can have a custom resolution specified in the gpu control panel, why is variable refresh rate a make or break feature for some? Couldn't you just benchmark the title you're currently playing, exit, then set the custom refresh rate to the average fps of that title, then turn on...