There's a famous Buddhist saying: First mountains are mountains and rivers are rivers. Then mountains are no longer mountains and rivers are no longer rivers. In the end, mountains are again mountains and rivers are again rivers. This describes three stages of practice. Before practice, practitioners may appear intelligent. They discriminate with a mind of attachment. The second stage refers to people who are practicing diligently. At that time they would not be able to make clear distinctions between this and that, and indeed they would appear dull or stupid to an outside observer. The third stage describes enlightenment, and once again practitioners clearly discriminate. The difference between the first and third stage is this: in the first stage people still have a sense of self. In the third stage there are no more attachments to self. Charles Luk was describing practitioners who were at the second stage of practice. To summarize, no, enlightenment is not a hindrance to the experience of intelligence. Indeed, it can even be of value. However, reliance on the intellect as a tool or guide to the practice itself can be obstructive.