They are not incapable of lying or falsehoods--what was their entire pretending to be Pure, ignoring the signs, if not that? But he is asking them directly, and to lie in such a way does not occur.

They nudge the blanket from their head, just enough to uncover their functional eye.

They do not nod. They do not shake their head. They understand the words of some, but the concept is unthinkable, and they don't know how to answer this as they are now.