When I was a kid, we played a game called keep away. The main rule was to keep away something that another kid wanted or needed. Like his lunch or shoes - something important. It was fun for about 3 and half minutes.
I think Medium is playing Keep Away with the bottom of the page. I noticed this months ago when I'd get 8 comments and 12 people clapping but only 2 reads on one article. Write to medium support - they said the arterial framus wasn't oscilating at optimum speeds and I should stop looking at the stats.
Since the bottom of the page signifies that someone read all of it and therefore you get paid _ I figured Medium was tweaking it so that, well, the bottom kept moving. Just a theory I think about along with the Lone Gunman.