Hi Cynthia,
Welcome to the Mattress Forum! 
Was it displayed on an actual coil flexing active box spring? That wouldn’t normally be the case. It would usually be placed upon some sort of a foundation that does not flex (which many people refer to as a “box spring”). The difference is described in more detail in the foundation thread here.
The bowed slat system allows for more flexing and sinking. If you don’t desire this, you could delete that system and place plywood decks (running side to side) across the frame network that comes with your bed. It looks to already have an integrated head to toe center beam as well as side lips. You could also choose to go with their flat slat system instead of their bowed system, which might feel firmer to you.
Phoenix