So maybe the window is bigger than the 6-7 seconds we all suggested. What is your issues here? What exactly do you disagree with? Nobody who is sprinting properly is going to hit their max velocity at 25 metres or 85 metres.
Most of your argument seems to come from improbable scenarios with really low level athletes. If we look at your scenario of someone being fully upright out of blocks after 3 steps then there are probably a whole host of things we should look at before worrying about how far into the race they hit max V. Removing the blocks would be a good start.