You didn't get it. There is a HUGE difference between VXGI and VXAO. VXAO is just a tiny part of VXGI which is a total dynamic global illumination solution that contains lighting, bounced lights and shadows, reflections and refractions caused by bounced lights, and AO resulting from it. The VXAO just approximates the AO from the game engine local lighting and casts AO according to it and this is nowhere as accurate as the results of AO rendered directly from full VXGI if the game has it.
The links I posted clearly show some tests of dynamic GI (VXGI).
Edit: I don't expect full fledged VXGI to run in such types of open world games. It is very demanding to run alone by itself.
Even HairWorks here look limited compared to other games that used it. No wonder that Turf Effects are limited too.
Running such techs at maximum like in tech demos would be not feasible on any current hardware. Maybe next-gen we will witness more ease to run them.
Also Turf Effects seems to be limited, it just displays more abundant grass with unnoticeable (almost absent) physical interaction unlike the intial tech demo (that is why I was doubting if the game has it and barely recognized the tech until I saw it written):
https://developer.nvidia.com/turfeffects