This means nothing. If the Grady girls and the old woman (“Remember what Mr. Hallorann said. It's just like pictures in a book, Danny. It isn't real.”) are visions that can laugh and speak how can you say with any certainty that Delbert Grady is not also an inanimate vision from The Overlook's past? He’s the exact same thing as there's no discernible difference in any of the cast members visions. If the Grady girls who speak to Danny aren't "real" as stated by Dick Hallorann how can the fact that we think we hear Grady speak be used to state that he's a real apparition. None of them can be proven to be real. It's all in the Torrances head's and the visions are directly proportional to each character's state of mind. Delbert Grady is a figment of Jack's imagination as he’s actually talking to himself in a mirror when they converse.