This is because of misinformation and misinterpretation. VRChat will try and use as many cores as possible, just so happens that some assets which VRChat does not control (such as Dynamic bones) only use a single core. As a result in some scenarios it appears as if VRChat is heavily hitting one core, when in reality it’s just Dynamic Bones doing this.
In fairness to dynamic bones, it was likely never intended to be used on a game of this scale.
You can use task manager to disprove the single core myth very easily by forcing VRChat to use a single core and seeing what happens in even just worlds where you’re alone.
If anything I’d probably suggest you disable Dynamic Bones in public lobbies and see how that goes.