Yeah, I wonder what their reasoning is to disable HTTPS on those tilde directories? The main site ( https://www.dtc.umn.edu ) supports HTTPS just fine (though it doesn't force a redirect to HTTPS, which is also odd/troublesome)
a. The web server hosting the tilde directories is very much likely older than the main site.
b. As any uni user can put any HTML on these directories Perhaps not supplying their certificate is an attempt to lower the success of phishing attempts for the main site logins.