Initially, any containerized process that requests ownership metadata of an object is told that its uid and gid own the object. Here is the relevant section of the documentation (emphasis mine): Ownership The osxfs driver on macOS tells a bit of a lie about ownership.
If you are seeing mounted files as being owned by root, your container probably is set to run as root. The osxfs driver pretends that the files are owned by the USER that the container runs as.
