On the Quest environment, it seems that VRCAsyncGPUReadback is not working. In the OnAsyncGpuReadbackComplete callback, request.hasError appears to always be true. (we don't have a way to identify what the error is, though)

This might be a known issue to the internal developer, but there is no mention of this in the document (https://creators.vrchat.com/worlds/vrc-graphics/asyncgpureadback/). Therefore, at least, please make a note of it in the document.

I hope this issue will be resolved with the next Unity version update.

(Repro: "VRChat SDK - Worlds/Samples/AsyncGPUReadbackExampleScene")