Ian,
You need to get specific here. Otherwise more general “more than one way to skin a cat” and “many roads lead to Rome” get brought up and we get lost.
We are talking about heavy sleds being promoted heavily (pun intended) to improve 10 yard dash times. If this was effective then we should see evidence. You provide your opinion and that is fine. I provide history and those times are facts.
Overcoming inertia can be address and is usually addressed by conventional weight training. Sprinting has been researched (along with sprinting and resistance training) to help sprinting. Heavy sleds have no research to be superior to conventional methods and no research has shown it to be the same. When people are weak and slow, training should help. I am not interested in research or methods that help neophytes get better since training should get them better! I am interested in methods that on average, provide safe and effective results that are consistently helping people in the majority of the bell curve.