There actually is empirical foundation for the communication of the effects![0] But the model is strictly simpler if you remove the astrology from it; astrology has no additional explanatory power, and its novel claims (claims not predicted by any other model) are wrong.
> Such children are more likely to be picked for school teams. Once they are picked, players benefit from more practice, coaching and game time — advantages denied to those not selected, who are disproportionately likely to be younger for their selection year. Once accounting for their biological age, the older players might not have been any better than later-born children when they are first picked. But after becoming part of a team, and being exposed to training and matches, they really do become better than later-born children who might be equally talented.
> Such children are more likely to be picked for school teams. Once they are picked, players benefit from more practice, coaching and game time — advantages denied to those not selected, who are disproportionately likely to be younger for their selection year. Once accounting for their biological age, the older players might not have been any better than later-born children when they are first picked. But after becoming part of a team, and being exposed to training and matches, they really do become better than later-born children who might be equally talented.
[0]: https://fivethirtyeight.com/features/why-athletes-birthdays-...