lmao.
> since rating systems shouldn't be compared anyway.
Yes, they shouldn't be, I agree, but visually, the authors made the wrong choice to pair them next to each other, so they unintentionally are being compared by the reader.
It's bad data vis. You're welcome to read Healy's book for an introduction to understanding data vis.
source: it's my part of my job to visualize data and write those kind of papers.