Charles isn't one who usually avoids the fact that he is a mutant, in fact, there have been a few conversations where he mentioned as much and probably should have been more careful. He appreciates Kate's sound thinking and will probably thank her for it later vocally rather than telepathically when it's not such a red flag.

He smiles, what a question. "I'm thirty years old, recently graduated from Oxford with a PhD in genetics." He takes a sip of his tea. "What were you expecting?"