The thing is, almost all of "gh" is an interface for GitHub: you can list issues, close issues, comment on issues, do all sorts of stuff with Actions, releases, your account", etc.
And oh, it can also do some limited stuff with git, kind of as an extra. Looking at the gh help output, the only commands are "gh repo {clone,sync}" and "gh pr {checkout,diff,merge}". I guess the repo clone/sync was added for completeness sake (other repo subcommands all relate to GitHub UI stuff), and gh pr is there because all of that is kind of non-trivial if you also want to be able to push to other people's PRs (not impossible or even difficult, just non-trivial and somewhat non-obvious).
In short, I think people are assuming a lot about all of this and there really isn't that much to see.
Fair. It is non-standard, published via Microsoft, and even named after the single product that it supports, but if we're splitting hairs it does technically have an open-source license. So I removed the term "proprietary."