Thanks to Steve P for pointing this out.
The chart below shows the 2011 IAAF A & B standards, and the number of male and female, Junior and Youth athletes who made either standards.
What does this tell us about the 400 meters?
First, note how the men’s 400m standard is doubled best 200m time plus 4 seconds. For women, the 400m standard is doubled best 200m time plus 5.5 seconds. That’s one mighty deceleration!
Second, even with the generous deceleration of the 400 meters, note how many women Juniors made the 400 meters standard compared to the 100 & 200m standards?
Zero. Zilch. Nada. Goose Egg.
Why is this?
In general, you rarely see a female 400m runner who can run even splits. That is, finding a women who is very strong and "not as fast over the first 200m". That strength quality doesn’t exist compared to men.
You may immediately think of Butch Reynolds, but he wasn’t a slow 200m sprinter.
But for women, they have to rely on speed reserve, which mean they all must have awesome 200m open times.
That being said, for the maturity of 400m development in females, you will find fast & young sprinters. Fast, strong & young is rare.
Perhaps coaches are hesitant in prescribing the butt-locking lactate training sessions for speed endurance and special endurance to teenage girls?
This is the main reason why I prescribe short to long training for young and developing sprinters. I rather focus on technique first, and add strength and power over the years. See the article on How to Run Faster… at any Age.