I believe it is not possible to do per-section permissions. These links seemed relevant and offer some workarounds in the tracker link:
- https://moodle.org/mod/forum/discuss.php?d=278444
- https://moodle.org/mod/forum/discuss.php?d=268618
- https://tracker.moodle.org/browse/MDL-38762
One idea I had, which is also mentioned in the tracker issue, is using section visibility settings creatively to control who can see what in the course. https://docs.moodle.org/33/en/Restrict_access_settings#Group_and_groupings
Using conditional access might work for you, in combination with using course groups. It might also be to kludgy for your use case, its hard to know for sure. Maybe try out the concept in a test course.