Theme settings? Ok, two things:
- The state of 'http' or 'https' is probably established in the sequence of things before the theme is loaded by /index.php.
- Why is it a 'theme' setting? Is it something that is to be styled or a part of the 'theme' functionality = no = its to do with how 'Moodle' as a whole works, therefore it is a 'core' setting.