Function
The course page reads the learner's enrollments to choose between Enroll and its enrolled state. Before the store is seeded — on the server, and for a moment in the browser — those enrollments read as empty, so without the gate an enrolled learner would briefly be offered Enroll.
Unlike CoursePageSwitch, the gate never swaps its children for another
page: it only waits.
Holds a course page back until the learner store is seeded, showing PendingCoursePage meanwhile (capability
course-detail-page).