Why does capturing Skarner spires alert enemy team (if they're paying attention)?

If you don't have vision of it being captured, why should you be getting that kind of information that the enemy jg is in that quadrant/location of the map? I thought the point of the removal of Tracker's Knife is to deny information; this is a contradiction. The map doesn't update for you every time the enemy jg clears their camp, the minimap icon stays until you have vision of it cleared. But what about tunnels you may ask. Well Rek'Sai no longer uses her ult to dash to her tunnels so in a way, so she no longer needs the knowledge if her tunnels are destroyed or not. Destroying her tunnels to give Rek'Sai information doesn't make sense, especially since you can sense nearby enemy champion with your tremor sense as a way to gather information.