Well, the no-header and no-footer classes are basically just quick tools to remove the header and footer section of the website. On mobile, the menu isn't really part of neither the header or the footer ...
You could add your own class to easily achieve this. Go to custom/css/, add the following:
.no-menu .sb-slidebar, .no-menu .sb-toggle {
display: none !important;
}
Then, in the same "body:" page setting, simply add "no-menu".