In my test installation (from fresh install), I have 2 courses, the admin user is a teacher of course 102. The other course has no teacher. When the admin is logged in, the admin is correctly displayed as a course teacher for course 102. However, when a student is logged in, the admin is shown as the teacher for both courses. Coursemanager setting is only set to teachers.
I tried removing the admin from the teacher role in 102 and assign the student the teacher role in 1.2. When admin logs in teacher of 102 is displayed properly, but when the other use is logged in admin is shown as teacher for both courses.