I think the study would be better if they used intra-rater control. First test the control and study group. Then repeat the experiment with the two groups switched.
What I wonder is if the WII group had a confounding factor - for example, they all had to go home and play video games from 7-8 or 8-9PM and then, because they were home, happened to get a good night's rest where the control group was not sequestered and stayed out, or on call, etc.
Still, it makes sense. Thanks for that!