The Problem - After following the "Multi-user Mode" steps for the DJI Goggles by connecting the Goggles to my Mavic first and then linking the remote controller to the Goggles, the "Max flight altitude" becomes 0 and cannot be changed, thus limiting how high the aircraft can go.
The root cause - I found this to be a firmware issue with the remote controller, thus needing DJI engineering team to fix it in the firmware.

Testing done:
I followed the "Multi-user Mode" steps for the DJI Goggles by connecting the Goggles to my Mavic first and then linking the remote controller to the Goggles. If the remote controller has firmware version v01.03.0700 or v01.03.0600, then there's no problem at all. If the remote controller has firmware version v01.03.0800 or v01.03.0900, then this problem occurs. During testing, all other things (Mavic, Goggles, DJI go 4 app) have the latest version.

I have also tested upgrading a remote controller firmware from v01.03.0600 to v01.03.0900. The result is from no problem to problem which confirms that this is a firmware issue.