Thanks for updating the title! I guess the author of the article got “fooled” by to. I just discovered this by accident. Now the debian.net redirects directly without the prior issue. Maybe they discovered this in their log and updated it quickly or it was a temporary issue with the certification.

Edit: To provide more context: https://docs.debian.net/scope.html

Any Debian Developer can host any Debian service they wish, wherever they want, and serve it through the debian.net domain.