The main difference between how instructor-paced and self-paced courses
work with respect to the outline on the backend is how we treat the
hide_after_due attribute on subsections (sequences). Namely, self-paced
courses ignore due dates even if they are specified on the sequence
(for example, by OLX import). If hide_after_due is True in a self-paced
course sequence, we only make it inaccessible after the entire course
ends.

This was tracked as BD-29 and TNL-7262.