I am not sure whether this story was originally written this way or has the story (and storyline) been changed ever since they knew the show would be cancelled, but the title was apt. Because the show featured behind-the-scenes happenings, it is rather apt to highlight the contribution of the prop people in helping run the show smoothly (or any show in that matter). One also learns that Cue-Card guys belong to this union. Some audience may not miss the three main actors (Perry, Whitford, and Peet) but they are the roles that shape the entire story. For this episode, their absence was all right because their "presence" was implied. Harriet alluded to Matt's character and her relationship to him during a good part of her appearance. I have seen them enough in previous episodes that not having any of them in just one episode was not a bother; as I said, their "presence" was implied.
The ending was interesting, when Cal asked Janney if she had the time of her life. Could it have alluded to Aaron Sorkin who, despite the show's imminent cancellation, might still have a great time doing this. If so, Janney's response was representative of what Mr. Sorkin had felt about this work. Inaccuracy: "1" is not a prime number (Simon mentioned to Claire [sp] that he had tried all the prime numbers, stating 1, 3, 5, 7, and 11; if he was going to list the first 5, then he should have started with "2": 2, 3, 5, 7, and 11).
As an aside, this episode reminded me of high-school productions when the director would on-purposely sabotage props to see whether the actors could improvise. In this episode, this would be demonstrated well by Janney who "offered her wallet" to the valet parking attendant (when she found out there was no prop money in it); while Tom played the role of someone who did not or could not improvise (by not helping Janney with the improvisation).