The bias, in numbers
Selection systems mistake physical maturity for talent. The piece cites a Dutch study of over ten thousand players where players born in the first months of the cut-off dominated the rosters and the late-born were massively underrepresented — because the older, bigger kids look better, and coaches, parents, and even the kids themselves reinforce the illusion. Development is non-linear, but selection acts like it's a straight line, so we gamble on the wrong players and rarely let the de-selected ones back in.
How I refuse to coach this way
This is personal to me because I believe every player, including the bottom of the roster today, should be treated like they could become great — and the late developer is the perfect example of why. The kid who's small and behind physically but reads the game well might be the best player I have at eighteen. So I try to separate what's maturation from what's actual ability, I protect the late bloomers instead of cutting them, and I hold to the idea of keeping as many players as possible, as long as possible. If I coach for the long game, I stop throwing away my future best players because they were young for their age.