Curiosity by itself does not improve intelligence.
It increases the chances of better understanding a given subject, given that curiosity is coupled with actions in that direction.
For example: I am curious about how to make pancakes and decide to find a recipe but stop at the first instance of an answer with steps to follow.
Curiosity needs to be coupled with the desire to improve a given understanding and be followed by a review of current knowledge with the aim of updating the previousely reached conclusions. Provided that the used logic that judges improvements is correct.
Curiosity will not necessarily be benefitial for an improved intelligence. But to allow for an improved intelligence, curiosity is a mandatory requisite.
Curiosity is a symptom of an evolving intelligence.