one can typically play video games for much longer than one can participate in physical exertion. The most a child is going to be able to run around on a field before getting bored or tired is probably a 2-3 hrs, and that's probably stretching it. On the other hand, if a kid is playing video games when they should be working on their school work, they're likely doing it for much longer, if not all night. I'm assuming, of course, that the children were allowed to play as long as they wished, or as much as they wished before a certain "bed time". I'm not sure of the parameters established by research group in order to make sure their experimental group was getting a degree of game time that would be indicative of what they were looking for.

But assuming both activities (organized physical activities such as sports compared to video games) are allowed to be participated in ad lib, there is little doubt that a child is going to be playing video games for a much longer amount of time.

In any case, as far as practical application goes, I think you're right, but I dont think it has to do with the nature of physical activity. I think it's just that a 6-9 yr old kid will spend much longer playing video games than playing baseball.