Hmmm, Docker Desktop is something people run on, well, desktops right? The official install is something aimed at people running Discourse on servers, where Docker Desktop is not a thing.
Discourse, as website software, is something people run on servers that are 24/7 on and connected to the internet so they are always up and can be remotely accessed by users. It’s different from local software, like Blender and Firefox that you can install on your desktop and use it.
While running Discourse on your desktop is used for development (and we have plenty of guides on it), running a production install on a desktop while possible will be too much of a hassle unless your are really comfortable with the technologies involved.