^Like I said, there is a real-world analogy in people with high-function Asperger's Syndrome. Even with extensive reading in the literature, they can still have trouble understanding idiom, social nuance, and the like. And they often have extremely literal minds. Bluffing falls into the same category as figurative speech: it's something where the information being presented on the surface conflicts with the true meaning underneath, and it takes an ability to read people and understand social cues and contexts in order to realize that the literal surface meaning is not the correct meaning. People who lack that ability are easily confused by such things as figurative speech, and probably bluffing as well. They can read about them all they want, but that doesn't mean they can understand them. Most people take their ability to understand such social nuances for granted, so it seems inconsistent that Data couldn't understand them the same way most of us can; but that's overlooking the complex levels of interpretation that are actually going on there. This is not just fiction; there are really people like this, who lack the social and emotional processing skills to decipher hidden meanings, even though their logical and intellectual processing skills may be far above the norm. They're two different kinds of cognition, so they don't always go hand in hand.
