Hi Dilina,
Thanks for testing the course format and providing feedback. I appreciate your time and effort. I have been able to reproduce the behavior that you describe. It is also fairly trivial to hide the 'Not Available' message that the course sections displayed to students when they section is hidden.
Martin and Anthony, I'm not familiar enough with Moodle to know which is the best approach. By default when a new course is created it is set to have 10 sections (this is some default value provided by Moodle). The weeks course format displays the week dates and a grey background when a section is hidden and the current user is a student. The topics course format displays the message 'Not available' when a student views sections that hidden. Should the timeline course format hide hidden sections from students? The advantage is that it would make things simpler for students, but would make the behavior not consistent with the other course formats that do display the hidden sections.
Linking back to the initial issue used to develop the specs and UI for the proposed course format which will be resolved as fixed. The actual coding work will be tracked under CONTRIB-1403. Let me know if there are any questions. Peace - Anthony