Apparently, they let a girl play in their league from age 5-10 (when there's not much differences between boys and girls, honestly) but kicked her out at age 11.
Perhaps they realized that around ages 11-13 that males enter puberty. And grow vastly bigger and stronger than females after that.
And that, upon that milestone, females competing with males is not only illogical, but very dangerous for the females.
Didn't stop Ellen Degenderless from having the erstwhile future feminist on her show, however.
Seriously, girls - You're got maybe 10 years to physically compete with boys.
After that, not so much...