I'd bet there is some exercise intensity threshold step function at work.
The article says exercise is, "only around 10 to 30 percent [of total energy expenditure] depending on the person (and excluding professional athletes that workout as a job)," implying that when you are doing lots and lots of hardcore exercise almost every day, it will use up a greater percentage of calories.
I recall another study -- no idea where I'd find it now -- which did body scans of runners. They found that runners which averaged 11mi/wk had substantial interior fat deposits. Runners that averaged 17mi/wk had very little.
The article says exercise is, "only around 10 to 30 percent [of total energy expenditure] depending on the person (and excluding professional athletes that workout as a job)," implying that when you are doing lots and lots of hardcore exercise almost every day, it will use up a greater percentage of calories.