> Hot tip: Use an ease-in animation to make the progress seem like it’s accelerating.
So annoying when websites try to deceive me with a quantified progress bar inversely inching towards completion even though I cut off Internet five minutes ago.
It's a challenging problem, because either attempts at a solution (being direct, or being indirect) causes a worse user experience due to expectations of linear progress. For example proposed solution 1 in the article would have you create some sort of animation or additional progress bar to let people know if something is actually stalled/dropped vs something just taking more time, you would still be lying to them, but it's for the benefit of user experience.
But the moment it's "wrong" it's annoying.
Progress bars for I/O are typically easy. Progress bars for computations with deep call graphs are typically more difficult.