Site Admins can access a Journal Manager's Journal Management pages (by going to Hosted Journals -> [journal name]), but don't appear to have proper access to the user Edit options. If the Admin clicks on a user role (say, Editors) and then clicks on the "Edit" link next to a user name, the following URL works:

http://git/ojs/index.php/test/manager/editUser/5

... but instead of the regular "Edit User" page, it's a "Create User" page, with all the fields blank. 

There's a workaround for this: either log in as a JM, or enroll the Site Admin as a JM. And this isn't a typical use case, so priority shouldn't be high. But I thought I'd submit it just the same.