Hyperbole of "jogging around aside" the rest of this is a valid question that I think gets at the heart of a common misunderstanding of training -failing to recognize that there can be a pretty big gap between the training we can physically complete vs. the relative adaptations we actually gain from it.
Training can be maladaptive without causing injury. Super-compensation is not a law of physics, it's a conceptual model used to simplify a very complex collection of biological processes. The collection of cellular signals we summarize as a training stimulus are not a mandate that the body will reliably follow, but rather a strongly worded suggestion for improvement. The capacity for improvement is dependent on the foundational fitness and lifestyle of the athlete.
The guys putting themselves through marathon demands regularly may be overreaching beyond what they have the capacity to adapt from. If we take a more extreme example this is an obvious problem -ultrarunners and long course triathletes have to train significantly short of fully race-specific demands. The tricky part about the marathon is that this boundary isn't as obvious and their is more temptation for overreaching.
The freshness aspect also shouldn't be ignored, it's certainly possible that part of this is just a training plan that allows people to express fitness better on raceday, and as you point out with the veterans some aspects of that fitness has likely been earned on previous "harder" training.
More broadly, often a hyper-specific focus on race-demands ignores how our physiology actually works.