I think time variability increases with the level of complexity. In this context I see the idea of task complexity being related to uncertainty in the time estimate. This makes it fit nicely with the Fibonacci sequence.
Time variability also increases with the time estimate for a task. If a task is "about two weeks", then it might be 1.5 weeks or it might be 4 weeks.
But if a task is about 1 day, it may take 4 hours or 4 days, but it will almost certainly not be 1 month.
Points are always just a proxy for time, and work the same way. Not matter what anyone claims, as long as you use points to plan time-abound sprints, points are directly a measure of time.
