It seems like there's a caveat here.

"Assuming similar active muscle mass, the athletes here training at 65% of their maximal oxygen consumption would have about the same muscular oxidative flux as an untrained person performing at or near VO2max."

So the high volume of low intensity training is, in at least one physiological respect, equivalent to maximal intensity training for untrained or less highly trained athletes. To me it implies that the polarized training model could be inappropriate below some threshold of fitness.