My problem isn’t as much with the statement in itself as well with the word “good”.
Let me ask a few critical questions:
What does “good” actually mean? He/she is running fast, so it must his/her good technique must be good? And if he/she run slow technique must be “bad”? Which comes down to: the fastest guy has the best technique? Remember the upright running style of 400 meter runner Michael Johnson. If he would have been running 48 seconds his technique would have been qualified as “bad”, but he ran 43 seconds so it must have been good.
How do you know his/her technique is good? (apart from that he/she is running fast) Do you have some kind of perfect model where you relate to? A kind of perfect picture or movie going in your mind of somebody running this prefect technique? Can we actually measure good technique by biomechanics research? Or is there a wide margin of variation within sprinters? Or maybe within different races of a sprinter?
And suppose the technique of the sprinter that you are observing deviates from this perfect model in your mind. In other words, in your opinion his/her technique is not good enough, what are the steps you take to improve it? Does this work and how do you know? Can you change or improve one parameter without changing other ones at the same time?
I remember having a funny discussion with another Dutch coach who coached a high jumper of around 2.28 m. He stated his jumper could jump 2.40 m if only he would manage to jump with a take-off angle of if I recall 37.5 degrees.
I asked him of 37.0 or 38.0 degrees would be OK too. No, that wasn’t OK. So, the perfect technique for him must have been within a very small margin. My obvious question: “how do you know his take-off angle is 37.5 degrees? (apart from the fact that he has jumped 2.40 meter then). Well, he could see that with his naked eye…….. well ……Ok….. I am not blessed with an eye that can see the difference of half a degree within 150 msecs, but I envy the people who can.
Bottomline: think again about the technical model you apply to our athletes, for a large part athletes sprint the way they do for a reason (anatomical, physiological or biochemical). Also in this aspect: there is no one-size-fit-all for every sprinter. “The” technique does not exist, we only know different solutions to solve a motor problem. Solutions that vary from repetition to repetition.