Its my understanding that the executor is legally required to execute the will as defined by the will or instructions from the deceased.
You are at least partially wrong. The will cannot exceed the bounds of the law. Every state (that I'm aware of) has an order that expenses and debts are paid. An executor cannot choose to not pay a debt simply because the will says not to pay it.
What do you need to know? It's a high school team, not the Olympics. Why wouldn't the default always be inclusion? High school is a tough time for a lot of kids, and I'd imagine it's more difficult for most trans kids. If participating in sports makes it 5% easier, then so be it.