If I’m understanding this correctly, this third party status page for GitHub is hosted on GitHub Pages and is powered by GitHub Actions…
I think you're correct. Kinda clever, actually.
Except if GitHub goes down the status page will also be down. Actually that is also indication of status so it kind works. :)
So technically Github is not missing a status page like this website claims: their status page is https://www.github.com .
As diabolical as it is, this is kind of fine; this site creates an aggregate stat from the existing status page, it doesn't provide an independent status page.