The Holy Daughter Writ was for helping Great Qin choose women with Phoenix Qi, and each region had to provide at least ten people. Of course, Great Qin wouldn't reveal its plan of gathering Phoenix Qi, so Zhao Fu couldn't make it too obvious.
Great Qin's conditions were that the women had to be between 12-45 years old, and this age range was quite great. Zhao Fu had originally wanted to set the range from 18-30 years old, and it was best that they were virgins.
However, after some recommendations from Xianru, Zhao Fu realized that he was still thinking like an ordinary person and was still bound by the rules of morality. As an adult and a ruler, his focus should be on benefits – only children talked about right and wrong. As a King, he had to think of Great Qin's benefits first.
Great Qin required Phoenix Qi, so anyone who could provide Phoenix Qi would do. Who cared what later historians would say about him? After all, history was written by the victors.