I think trait curiosity probably is a real-some-sort-of-mental-phenomenon, so I wouldn't go so far as to say it is not a thing. Please also understand that I am no expert on trait curiosity or personality in general. Still, I tend to lean towards thinking that most people really mean state curiosity when they think about an actual drive or desire to figure something out. But I am perhaps biased because I investigate state curiosity and leave trait curiosity to others.