In a single-activity format course, the course navigation block disappears in the settings or reports, such as the participants page, gradebook, "Edit settings", question bank, or course completion report.

To reproduce, create a course, under the "Course format" settings, set the Format to "Single activity format". Ensure you are using the Boost theme. On the course main page, note that the course navigation block is present in the upper left column. Go to the participant list or question bank for this course and the course navigation block disappears.

I would expect this block to remain present on all course related pages, including settings and reports, just as with courses in the Topics format.