Yes, I'm aware of what they're saying. It is indeed the default for most VR applications. I can't think of a VR application that uses a global volume for voices; it's all local and diminishes based on distance from source. A universal volume for anyone on a map is weird and awkward, and most game engines have sound differ in volume based on distance and location by default. Most VR applications, even the "professional" ones, are built on top of game engines, because it's a lot easier than writing everything from scratch.