What are these dark dots on the time line? Are they necessary?
They divide the timeline into equal segments to denote time and duration.
And they don't interfere with the skip? And what's the practical purpose for the user?
It has nothing to with seeking. It’s just a visual indicator.
The purpose is to help give you an idea of duration by giving marks for each 15 mins or 30 mins depending on the length of the timeline.