(some) Learners completing courses in 5 seconds

If the course is important and they need to learn, then you have some sort of means to measure their understanding to prove the learning. 

You could put places where people interact with the content and allow their proof of understanding dictate how they move through the content and complete the course. I used to put assessment scenarios up front. if they passed they moved on because it showed they know the content. if they didn't they went through the content.