Your problem is that although your commands (either your first option of creating an orphan branch and pushing an initial commit, or just deleting the Git repository and creating it afresh) delete the history in git, they don’t delete it in GitHub. GitHub (the website) stores, independently of Git (the version-control system), the previous forks and branches that are no longer part of the repository.

If you look at your https://github.com/XXXXX/YYYYY/tree/c7acde... link, you'll notice a message at the top of the GitHub page saying “This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository”. This is because the commit is stored by GitHub, but isn't part of your Git repository.

As far as I know there isn’t any way of deleting permanently a Git commit from a GitHub repo, even after it’s been deleted from Git. Your only way of truly purging all history from GitHub may be to simply start a new repository, copy all the files, delete your previous one, and rename your new repository.