Hi Chris, the bees will expand their hive into the honey super. By adding a honey super, we suddenly increase the space available to the bees, so as you can imagine, they will just naturally use that space to increase their brood & stored honey while the conditions are favorable for them to do so.
Just a little side note: They don’t view the QX as a barrier to the queen. They will prepare the comb & leave it empty for her to lay in just as if it wasn’t there.