These are the type of discussions that I enjoy. A few years ago, I was was very black/white and by the rules with my animals, and would have had much the same reaction as many of the others who have replied in this thread.
However, in those few years, I've had the opportunity to speak to different well respected breeders and hobbiests and you know what? No two did things exactly the same! There are no hard, fast, consistent "rules" if you will to keeping and breeding ball pythons. There are guidelines that are generally considered safe to share with those new to keeping ball pythons or new to breeding them.
The longer you work with them, the more you learn to read your animals. This is not Bill's first season breeding. That female WAS in her third winter, and I have no doubt that if Bill felt her body condition would put this girl at risk when he made the decision, he would not have bred her.
I've seen others who thought outside the box and pushed the limits. It was Jasballs who got even the big breeders to re-consider the weight that they first bred males. Like Bill said, a few years ago, it was unheard of to breed males less than 800 grams (he said 1000, 800 was the "rule" I was told). Now Larry and BT talk about breeding smaller males, I've heard Ralph talk about breeding younger smaller males, and many others.
It took one person to understand their animals and read their animals and be willing to push the envelope to change the entire ball python breeding industry's way of thinking.
I'm not in any way suggesting that a new person in their first or even second year of breeding should take a small girl and breed her. I'd still recommend to someone new to stick to the 1500 gram minimum, as to recommend any smaller to someone with limited experience reading their animals would be reckless on my part.
However, I have no problem with those with more experience sharing their experiences with us. That's how we grow, how we learn.
Kudo's Bill! And I hope you hit on those odds!