I’m not involved in this project, but I would guess that it’s because it validates both issues and PRs, but only PRs have statuses on GitHub, More precisely, only commits have statuses, and issues aren’t associated with commits.
This is exactly correct. I haven't finished the pull request feature yet, what you're seeing on the repo is just issues. I will be taking requests for any desired features
“avatar_url” is the only part of that endpoint in preview, so that warning only applies to that field. I can see how the notification isn’t clear on that point, and I will bring that up.