Bud growth in flush

Possibly drawing in nutes from the last remaining leaves and producing more bud, but its entire focus now is trying to be pollinated, so it's probably putting everything it's got into keeping the pistils alive. That said, look into the effectiveness of flushing. Flushing is more "ancient grower wisdom" than scientific reality. It doesn't seem like there is any benefit to flushing other than stressing the plant out which, like grapes, could have some flavor profile effects. Blind taste test studies I've read have concluded that people actually prefer the taste of unflushed bud and there is not difference in harshness.