"You already understand", "the answer is right in front of you" or words to that effect are often found in Zen dialogues. These words are often used by a zen master when an advanced student, who has spent much time studying and practicing Zen Buddhism is stuck on a koan. And often, the student is immediatly enlightened, or rather, realizes that he is already enlightened.
While I am not an expert on Buddhism, or Zen, I would say that perhaps people have read too much into these types of phrases.
For example, if Zen Master Ma Bo says to his student, Fu Jiu "you already understand", it is probably because he has been training with that particular student for several years or a decade. He knows the students background, his progress, and his mental habits. He knows that the student has an adequate level of spiritual and intellectual maturity. So when he is addressing the student, he is specifically adressing him, at that moment, which was hundreds of years ago in a very defined setting.
However, many people who studied these collections hundreds of years after the fact, on a continent and lifestyle far away from what these texts refer to, think that when a Zen Master says this sort of thing, he is telling anyone who may happen to read his words that they already understand. So then the reader, sitting in a library or a dorm room hundreds of years later, looks in their immediate consciousness and tries to find what, exactly, is in there that qualifies as enlightenment or absolute truth. And, if they are anything like me, their thoughts are mostly about that cute girl that sits next to them in math, or the bills they have to pay, or How old is Wolverine, anyway. These are not the thoughts that the Zen Student had in his mind when the Zen Master spoke to him.
While I don't want to downplay the fact that many of the Houses of Zen have believed that anyone can undergo immediate enlightenment, the way in which they reach it can be different for anyone. Zen Masters would use different tactics with different students, and probably could have never guessed that a thousand years in the future, waiguoren would be trying to apply the private discourses between them and their advanced students as a blanket statement about everyone's level of consciousness.