Very simple. The 10m mark sometimes is hard to see in meets but in practices a lot of coaches use the 110m mark and see how the steps look over 10m. Most elites in 100m dash take about 7 (+ or- .2) and the yards is about 10% of elites and that is usually 6.5 steps. Sub elite guys are not taking 5 period.
the 5 for 10 is a myth and even a half step difference over 30 feet a huge difference when we are talking the cream of the crop that have hit an asymptote of performance.
Having kids tying to hit those marks is foolish and borderline dangerous.