You are very observant and noticed the small errors in the ANN. I usually just type mixtum.io and access the official website to use MixTum's services. Maybe I'm just a regular user so I haven't had any problems with http and https ^^
Its about the onion link.
When you use clearnet, it doesn't matter if you entered http or https in the browser, you will always be redirected to https. That's why you don't have a problem because everything is fixed on the fly.
I'm not very familiar with the TOR network backend, but isn't there some way to redirect all access to the site to the active version, regardless of whether it's http or https. Something like an htaccess file on a regular web?