To use a trivial example, if you're competing in USTA youth leagues in the younger brackets and you haven't completed puberty yet, you're going to get crushed by the kids who have - no matter how hard you work, no matter how hard you practice, an 12-year-old who hasn't hit puberty will get demolished by someone who has completed puberty, OTBE.

That was me!
My mother insisted I start school a year early. At 15, I believe I was the youngest in my high school class, and among the smallest. Too small to compete in baseball/football in Los Angeles high schools, I would have spent those years on the bench.
But tennis I could play. I figured that if 5'6" Pancho Segura could hold his own against 6'2" Pancho Gonzales, I could hold my own in high school. I got dusted by some very large seniors who went on to get UCLA and USC tennis scholarships, but it was a thrill to play with guys who could hit that hard. I survived thanks to copying Segura's 2 handed forehand, especially on return of service.
There were no girls on our high school team who could have won in the boys division. There were many high school boys who would have ... and I am sure of this... dominated every match in the girl's division.

But that was before any kids were using drugs to make the change, so I don't know how that would factor in in a super competitive city league.

I do know size matters. Even in surfing, the average size advantage of men allows them to paddle faster for superior position. When the wind blows hard offshore on Maui, a Laird Hamilton at 6'3" 215 lbs can overcome that wind in his face while a 5'4" Bianca Valenti's 125lbs gets blown right back over the top of a big wave like a feather in the wind.

Nobody likes to lose when there's an obviously unfair advantage. Competitive sports will take some additional consideration.