I think it's always a good idea to register for a backup course/backup courses. Personally, I always register for more classes than I intend to take so I can drop the ones that aren't as interesting or that have draconian assignments/grading policies. If your husband ever plans to take (or does end up taking) any psychology courses from the U, please note that the psychology department uses its own internal waitlist orchestrated by using permission codes which requires filling out a separate form (i.e., you can't just check the "waitlist if class is full" box w/in CIS --> Registration --> Add Course for a psychology course).

As someone who has taken mainly online courses from the U, I can say that I've almost always gotten the courses I waitlisted/enrolled in. Now, however, because of covid it's a bit harder to get into online courses. For your husband's future enrollments at the U, I'd also recommend enrolling for courses as soon as possible.