Nvidia adaptive vsync doesn't work in windowed fullscren mode, but it does work in normal fullscreen. In other games it usually does work. I do not remember it ever working in Arma 3. See attached images.

Windowed Fullscreen:

Normal Fullscreen:

It would be good to have this option to enable vsync but avoid stuttering when fps drops below refresh rate. In Arma 3 it is common for some scenes to render very high fps (menus, VR map) but then other times the FPS falls below refresh rate.

Advantages of adaptive vsync are reduction in power consumption, heat and noise from GPU without running into stuttering issues inherent to normal vsync.