Percy didn't want to argue with Cass. There was no point, and he didn't point out that the circumstances of Cass's distraction were so unique that they'd never happen again. Instead he hold Cass tighter, because that was easy and made him feel better without having to open his mouth.
"We'll go home soon, Cass, and then you worry about getting better. That will make me happier than anything else." He kissed Cass's forehead. "You don't have to do anything other than not lying to me. That's all. I liked that annoying pain in the arse who never left me alone, no matter what I said. I don't need you to become something else."