Honestly, I'm a liar.
If Bergman threw on a cute little summer dress, chose a different identity, and grew out his hair, he'd win every female tournament there is.
What's to stop this from happening? This could have been happening for years and years and years. But it hasn't been. That I know of, no top player or anyone even close to a top player has changed their sex to make easy money. So, why hasn't it happened? The answer is obvious but apparently not to everyone.