I doubt many other reviews will view it as enough of a difference to make the scores differ, but I can definitely see where they're coming from.
As for why a change in gameplay score was enough to change overall, if you look gameplay is one of the few things getting it to the overall it has. Lasting Appeal is 10, but the three other scores are all 7's. If the idea is that they decided gameplay is important enough to make the review a 9.0 instead of the average which would be an 8.0 than if gameplay is change I would expect it to have an unusually large affect on the overall.
...









