They're mixing and messing definitions and concepts and separation together and then get confused because of it. It describes a behavior analysis discovery but lacks the useful, valid discovery. I don't think this is useful for others to read, and detrimental for git newbies, because it's more difficult and confusing than helpful.

• git says HEAD defines the current branch
• rebase is a process operating on commits and branches - it breaks out of the simple "current repository state" because there's a process and process state around that. They notice things being different, but fail to elevate their view or discover that they have to interpret it differently.
• bare repository has no workspace - as such, workspace commands won't work, and there is no workspace current branch. HEAD defines the default/main branch.