On this page in the VisionOS Documentation https://developer.apple.com/documentation/visionos/adding-3d-content-to-your-app there is the following broken link:
For more information about when to use volumes, see Human Interface Guidelines > Windows. https://developer.apple.com/design/Human-Interface-Guidelines/windows#visionOS
Leading to "The page you’re looking for can’t be found."
Hope that helps.