The way Kalliope phrased her question might sound rather ambiguous, however Prince Revaz directly knew from the first sentence what she truly meant and despite knowing that the chances of him successfully distracting her was basically zero, the second prince still gave it a try.
He pretended not to realize what she was asking and just answered the other things. It was because he didn't wish to be the one who told her the truth. For some reason, his instinct was strongly telling him that the news would leave her more devastated than the enemy tricking her.
But, to his dismay, Kalliope insisted on hearing what happened. "How were they able to confirm it? Despite the contract, the host's mana isn't fully converted into dead mana. So, the traces of black magic shouldn't be obvious, especially when the host original power is of earth magic."