You're not "saving me here", you're just confusing people. That is, I'm talking about what is known from research in exercise physiology, whereas you're talking about it's weak cousin, #sportsscience.
In essence, your argument is that if you knew the length of each of the "legs", for a given individual, you could use that information to optimize training. Unfortunately, it doesn't work that way. Instead, you should train to meet the demands of the chosen event.
IOW, even a 1500 m runner with a high VO2max will still benefit from emphasizing appropriate intervals at the appropriate time, just as a marathoner with a high relative "threshold" would still want to put most of their eggs in that basket. Every runner should include a bit of training specifically aimed at running economy, but since 1) running alone will improve it, yet 2) it isn't as trainable as the other two "legs", it should never really be a major, specific focus.
At least , these are my conclusions based on >50 y of both studying exercise physiology and participating in endurance sports (including distance running).