It gets deeper: they even throw gender into the mix, and discovered that male brains seem to be working harder to do this kind of "mind-reading" of the other side. Their conclusion says that that's because women are naturally more empathetic, and thus don't have to work as hard to figure out what another person is thinking. That seems a little general -- it could also mean that the males care more about competition, and thus are working harder to "mind-read," or it could even just be a wrinkle of the way this data was gathered. More research is probably needed on that one -- if women are so great at figuring out their opponents, why aren't we seeing all-female teams winning Arena tournaments?
It would be interesting to know, too, whether there's increased activity in other areas, say pattern recognition or cause-effect centers of the brain, when we're playing against opponents that we know are computers. But this does tell us that there are definitely different skillsets at work when playing PvP or PvE, and why some people might very clearly enjoy one over the other.