Not mentioned in your story is birth month of your two daughters, and how that aligned with the sports season. Its been shown that there are a greater percentage of summer birthdays in professional baseball, as an example. Older kids in the age group (particularly at young ages) have a developmental advantage going in compared to younger kids, which can result in more reps, more opportunities to improve, and more playing time. This all compounds over the youth years.

https://slate.com/culture/2008/04/why-do-so-many-pro-basebal... https://www.sciencenewsforstudents.org/article/why-many-olym...