Surely that stat is influenced by how many minutes a particular team was (not) in possession of the ball.
Unless that's been specifically factored in and then comparatively averaged out, that stat will be a skewed representation of... well, nothing of any value.
*edit* And the stats were unsourced....
In general I agree but these are the only stats I could be bothered putting together (feel free to source your own stats if you have any theories of your own you'd like to put forward). It ultimately doesn't matter because these stats reflect what happened, rather than why. Players who attempt few tackles are either not targeted or they are not involved. In the case of halves, they are all targeted, even if some are targeted more than others.
But if it interests you, the Storm attempted far more tackles than any other team, indicating they got numbers into the tackle more than everyone else (so three guys tackling one runner counts as a tackle for each of three players, counting for three total team tackles). This would also account for the high tackle percentages of Cronk and Green, because they were less likely to be attempting their tackles alone. As always, use context to interpret statistics, and if you're unable you are always free to ask someone who can.
The Storm (individual players combined) attempted 9857 tackles, which was about 7% more than the next best Cowboys and third placed Broncos. The lazy Warriors attempted the fewest combined, with only 8054 combined tackles, meaning they were the team most likely to leave their mates isolated in defence. Interestingly the Storm forward pack has a high number of New Zealanders.