Thank you for looking at the data, so I don't have to!
My suspicion is that they introduce a lot of chaos into the system, varying things up a lot by article, month, etc, so we don't revolt if they DO reduce payments or otherwise change the payment structure.
Medium is not a money maker for like, 98% of us. Anyone who says any different is trying to sell you something (probably their "90 day success on medium" course or some such nonesense). Sure, there are outliers, but most of them joined circa 2017/18 when things were different and new.
I come here to make like-minded friends (the best benefit!) and a little pocket change, that's it. Of course I've never been anything even approaching consistent on this platform, because for me the money just isn't worth it. I write when I have a sudden desire to express myself, and that's it.