I tested running the game with the G-Sync indicator enabled just to check and noticed that it wasn't being activated, so then I tried manipulating the system sound volume and sure enough the game wasn't running in exclusive fullscreen.
From experience I know some APIs have the workaround to enable V-Sync in the software, and confirmed, then it showed G-Sync being enabled and no volume indicator showed up anymore, confirming exclusive fullscreen.
This however means that you can't combine the API with V-Sync from the driver (Nvidia Control Panel), which supposedly is more optimized for use in combination with G-Sync.
With all of that out of the way, I really appreciate this project, so thank you.