The problem is that we have already spent too many seeds (some of them literally wasted), I´m just saying is that for achiving victory here we NEED to keep Sayaka, Kyuko and Homura alive (because if any of them die is Game Over), and if we are so low on seeds when Wallmart are barely injured
We can´t afford waste anymore, and the second part it´s also merely practical, what would be worse, the bewitching of Akane or of any of the ones of Tokyo?
Thats why the risks that we have leaving Sayaka or Akane short on seeds is vastly superior of having the girls in Tokyo short on them.
Maybe it´s because I´m studying Economics, but the only thiking behind this is to reduce risks