Is it expected behavior for child groups to be auto-enrolled if enrolling a parent group to a course?

Yes, it is expected behavior when enrolling a Parent group into a course that all members in all child groups are also enrolled in the course. The users will appear in the “Enrolled Students” section, however the child group names will not appear in the “Enrolled Groups” section.

Additional Trainings

Enrolling Students and Groups in a Course or Curriculum

Group Enrollments: Enrolling current and future members vs. current members only

Why can’t I remove a student from a course or curriculum?