The thing that disappointed me the most about Magness's response was his insistence on periodization / complexity to get that final 1% of performance or whatever. Sage mentioned periodization also and how to prepare for a marathon one must do some hard long runs, etc.
Spoiler alert: a special marathon block is a part of it. But I almost wish it wasn't, just to show what kind of performance one could achieve without it. Sirpoc went from >21min 5k runner to a 15min 5k runner on NSM. Before the marathon, he did a handful of longer, more marathon-specific sessions and he lengthened his easy long run. And then proceeded to run a 2:24 on a warm day when many other more experienced marathoners blew up. As long as you zoom out on the training, it's obvious that 99.9% of what contributed to the 2:24 was the years of NSM.
The "special marathon block" didn't provide any transformative physical adaptations in the last moment like some insane durability / resilience / fatigue resistance that years of training on fresh legs failed to develop.
The "value" of training on tired legs is so misunderstood. As is the "value" of doing a huge, exhausting session. Non-elites have zero business doing either of these things. There's no value in seeking them out. They're a consequence or a side effect of elites pushing the limits to seek the highest levels of fitness. At that point, there can be value in doing sessions despite how fatigued you are going into them and how taxing they are.
But for everyone else, even sub-elites, it's absurd to be purposely violating the basic premise of training: do a workout, then recover and adapt to it before you do another workout. There's no special hidden adaptation that you get that's worth undermining this basic cycle of training. And while you can "weave" different stimuli that have different "recover and adapt" timelines in some complex dance, the fact is that for beginners, hobby joggers, and even sub-elites, the one overwhelming factor that matters more than any other is aerobic development. So the most surefire way to improve is a repeatable, not periodized, finely tuned cycle of doing a workout that advances aerobic development, recovering from it, and then doing another. All other routes to improvement be damned, as they either get slowly developed along the way despite not being the emphasis, or they're too small a factor to be worth prioritizing until much later.