Thanks for your question. I am honestly not sure why the site is being blocked. If it is harmless then it certainly shouldn't be blocking. I've taken the liberty of forwarding that site on to the appropriate team to investigate it and whitelist it on our filter if applicable. I'm glad to hear adding it to your allow list resolved the issue for you and I do apologize for any hassle it may have caused. If you need any further assistance just let us know.
Thank you and have a great rest of your day.