Rasplex Installation instructions instruct to 'run as root with SD card inserted and unmounted'

> run as root with SD card inserted and unmounted

[What does this mean](https://www.rasplex.com/get-started/rasplex-installers.html)? How can the OS start without mounting the SD card?

<img width="1220" height="407" alt="Image" src="https://github.com/user-attachments/assets/41b4e340-5e42-46fa-a573-f3f063f05e7b" />