He'll realize later just how weird the disconnect is between what Giles is saying and his tone of voice, but in the moment he's not noticed. Even if he did it might not have changed anything, Pratt is so hyperfocused on Giles' words that the cadence of speech and facial expressions are practically invisible.

What have I told you about hesitating?

Pratt grunts and breaks his eye contact with Giles to look over his shoulder at something that isn't there. And then back down at the man he's knocked over. The knife is still in Pratt's hand, he's close enough he could stab him right in the throat. But...

"Who are you, and why do you keep threatening me? Is this a trial?"