Malbim: The verse does not count when Hashem appeared to him at the beginning of the building, for it was not a total prophecy. "Va'Yhi Devar Hashem El Shlomo" (6:11) is a small level of prophecy, like the Ramban writes (Moreh ha'Nevuchim 3). Here and in Giv'on were absolute Nevu'os.