They mention that as a mechanism for protecting the SSH keys for the repo.

Essentially using a repo that doesn’t matter with the coding agent and then creating a cross-repo PR to the real repo.

I believe the author's idea is to do dev work from a Github account that only has access to the fork, but not to the main repo. Then, as a contributor, you'd open PRs from your fork to the main repo. I think this would only work if your Github account doesn't have write access to the main repo, though. I know you can use 'deployment keys' to give read-access to a single repo using an SSH key, but not sure if you can otherwise restrict access to a single repo with write access. Essentially, though, you'd want to find a way to give the remote host the most limited possible privileges to your Github account.

Spammy ai-generated self promotion.

If the Claude (or similar) can't open a browser on a headless server, they typically print a URL you can copy to your browser on your local system-with-GUI. From there you authenticate and get back some kind of token, which you copy and paste back into your remote SSH session.