USA Soccer is based on the European model of soccer development. You also are usually required to not play any other sport in their top clubs and academy teams. USA soccer is over the top in their quest to compete against the European countries with 10 times less people.
Going by a 9/1 Birthday or maybe 8/1 is close to the start of majority of schools in this country and keeps all kids in their proper age grade. Common sense says that is best solution.
My son plays on an academy team and also plays lacrosse and basketball. No issues. Ties in events go to the “In season” sport. The coaches get pissed from time to time. If they don’t like it, they know they can bench my kid. But they haven’t yet.