Fic idea: Kryptonians are incapable of lying. It’s not built into the biology, it’s just not. They can mislead, can imply, can refuse to answer, but are incapable of speaking a deliberate untruth.
The first time Clark remembers ever noticing was when his teacher told them the story about George Washington and the cherry tree.
He related the story to his father later- "just like me!" He'd said. Up until then, his parents thought that he was an honest child, as good natured as he was in all other things.
They teach him all the ways to hide it, to keep his too-dangerous truth to himself in a mouth that can’t lie. He learns how to phrase things just so, when to not answer, and when to tell the truth. The truth is the most unbelievable part of all, and in the right tone it can’t hurt him.
It makes him a better writer, a better reporter. Maybe truth-telling is built into the Kryptonian DNA, he’ll never know, but something about all the secrets he has to keep makes him want to tell the truth wherever he can.
As a reporter, he’s scrupulously honest, is known for it. He wants, needs, to unveil all these truths in his work.
His interview with Louis is the riskiest thing he’s ever done, but he wants to do it. People are afraid of him, and he knows by now how much a lack of information can be more terrifying than any truth.
Clark was a reporter- he knew how to manipulate a story. He didn't have to lie to let Lois think he'd only come to earth recently, that he had no other identity, that he was as alien as he often felt. He’s been practicing for this his whole life.