A progress meter may not be necessary, but as the article points out if you have comments or an otherwise large footer not associated with the content of the post, the scrollbar can be deceiving.
I'm personally a huge fan of the progress meter (having once thought it was redundant as well) - one other easy addition I didn't see mentioned is an "estimated reading time." Having a ballpark range for how long I should expect to spend with a piece of content greatly increases my chance of engaging with it, and the progress meter creates a tangible representation of that time (and how much of it I have left to finish consuming the content).
I'm personally a huge fan of the progress meter (having once thought it was redundant as well) - one other easy addition I didn't see mentioned is an "estimated reading time." Having a ballpark range for how long I should expect to spend with a piece of content greatly increases my chance of engaging with it, and the progress meter creates a tangible representation of that time (and how much of it I have left to finish consuming the content).