Is there an official way to time? The first step they take? Swing of the bat?
In the past even college coaches disagreed with a common method to time the runners. I sat thru a debate on this trivial subject listening till I was ready to fall asleep. I don't think they ever established a standard.
Just for fun, we used to have the girls stand in the box and yell swing and started the stopwatch when they broke to take their first step. If they batted right-handed, they started in that box, left-handed the left box. It is what it is.
I had a coach from Arkansas years ago tell me if I found him a girl that could run from home to first in 2.3 seconds he'd give her a full ride and he didn't care if she even knew how to play softball. He'd teach her how to get on base. Now I took that for what the message truly was. Speed kills in this game. You'd better be able to hit with power, or run like a deer, or spin a pitch around a telephone pole if you want to play with a top-rated team. All girls at that level throw hard. nobody cares....
Years ago, I think it was UCLA had a girl show up late in the dugout during the college World Series because she had to finish running in a track event before joining the softball team.