I find Rtings confusing on their ratings, as well. They're generally really perplexing in monitor reviews. They can take two displays with similar local dimming systems and panels and rate one a 2.0 and the other a 7.5.
I don't know if they go back and rework the numbers on their older reviews but in just a few years local dimming has gone from a couple of zones to hundreds on the higher end model so the scale has changed a lot.