How many narratives use comparative strength data as proxy for adversity, for pluck, for character? Look closely and (I promise) you find the data is garbage which then turns the narrative into garbage. The better authors handle the data gingerly, with care, who know not to place loads where they can't be borne. The better authors are scarce.
On the other side, we get authors who are crazed by the imagined disparities they see in comparing sets of false data and who work to share their rage with the reader. This can spread from one (false) view of a battle into a generally false picture of the war and the men who fought it.
I would like for him to give more examples, besides forced marches, of what he means. I think it could be interesting and he's probably on to something. The example of forced marches was kind of lost on me. I understand what he is saying about them and he has a point but...
The hard marcher gives this up and disorganizes his own units for some gain or other. He has to know what that benefit is and he has to be right or he is bordering on relief and/or court martial.
I think Jackson knew what the benefit was and he was usually right. Keeping up with the hard pace of Jackson's marches became a product of unit pride for his brigade. And this on top of achieving his objectives.