Certainly Cognitive Therapy would agree that an individual's expectations are important and that experience plays a major role both in their development and in modifying them. Beck would also agree that this is reminiscent of George Kelly's work. He credits Kelly, among others, as an important early influence.
However, even if everyone agrees that expectations and experience are important, I don't see how this implies that it makes no difference whether we focus on experiences within therapy or on experiences outside of therapy. We'd argue that, in general, focusing on real-life experiences in the here-and-now is the most effective and most efficient alternative but that at times it is important to focus on experiences within the therapeutic relationship and that at times it is valuable to focus on family of origin experiences.