Last evening, when I removed the stopper from my Pharos, I noticed that a screw is inserted into the bottom (from the thick end); and I fell to wondering why. Perhaps it's there to stiffen the stopper. Does anyone know what the point of it is?

Some without the screw might mention how irritating it is to have the stopper stuck inside the lower chamber from being inserted too far by accident. My guess this was to help with that.