I suspect they mis-interpreted that part but admittedly I haven't listened to the whole thing. The reason there is such a big difference between below average

I suspect they mis-interpreted that part but admittedly I haven't listened to the whole thing. The reason there is such a big difference between below average and low is because in the "low" group, there's almost certainly something wrong with that group. A heart/lung condition, cancer, morbidly obese, i.e. issues with major body systems.