To further clarify – that section pertains entirely to the VRR range (Variable Refresh Rate range) being used by G-Sync (and possibly FreeSync, I guess) while playing the game.
Without Special K, the game requests a 60 Hz refresh rate, which typically controls the upper limit of the active VRR range and where V-Sync is supposed to kick in. For most games Nvidia’s drivers should override the requested refresh rate with the highest available of the monitor (e.g. 144 Hz) – which is controlled by the
Preferred Refresh Rate setting in Nvidia’s control panel.
In some games, however, Nvidia’s override doesn’t work properly, and so instead of the VRR range being the full range of the monitor (0-144 Hz for example), it’s capped to the refresh rate requested by the game (in this case 0-60 Hz). Using Special K to override what refresh rate the game requests then allows solving that issue, and instead of 60 Hz being the upper limit of the VRR range, it can become 144 Hz (or whatever is the highest supported refresh rate by the monitor).
Edit: I’ve rephrased the section on PCGW.