It's actually the opposite. January and February are the highest above and for hockey, because these kids are usually more physically developed than peers. This leads to being selected for elite camps/teams earlier, which compounds throughout their lives. Another cool economics type phenomenon in soccer (may no longer be true), a study was done early 2000s, there's a perfect balance of wealth of parents on average for professional soccer players in Brazol: enough that their nutrition is never sacrificed, but not enough money for structured programs after school, means they're fit but also non stop playing street soccer.