If you're using github pages you should just structure jekyll such that you can edit data/_links.yml instead of having thousands of users wasting compute power for github api when its not necessary
I would suppose doing a push every time a new URL is added would be quite expensive for GitHub too. Plus, GitHUb pages is not updated immediately upon push and it takes some time for new links to work. That being said, this is definitely not the most realistic implementation of a URL shortener. It is meant to be cool and hacky and definitely not used for production!
