The site administration settings provide a setting for whether or not "Guest access" enrolment method is to be added to new courses by default. Unticking the box has no effect; the method is still added to new courses.

The corresponding setting used for Manual enrolments works as expected.

Steps to reproduce
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1. Login as Admin and go to Site Administration > Plugins > Enrolments
2. Click Guest Access and untick the "Add instance to new courses" box
3. Click Manual enrolments and untick the "Add instance to new courses" box
4. Go to Site Administration > Courses > Add/edit courses
5. Add a new course
6. Enter the new course and click Course Administration > Users > Enrolment methods

Expected result
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Neither "Guest access" nor "Manual enrolments" methods should be listed.

Actual result
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"Guest access" method is listed, "Manual enrolments" method is not.