How does Google know what components to expect?
Ultimately, the list of components for a movie comes from its manifest. But even before you deliver the manifest for a movie, Google can derive a preliminary list of components from the information in your avails.
The avails identify which cuts of the movie you're offering and which territories you're making them available in. For each cut-level ID and territory, Google checks to see whether you've previously delivered an experience with the same cut-level ID and territory (either a Region element that includes the territory or an ExcludedRegion element that excludes the territory). If you have delivered a matching experience locale, then you've fulfilled that portion of the avails.
If you haven't previously delivered a matching experience locale, Google populates the Experiences page in the Movie and TV Partner Portal with a blank experience locale. It also populates the Components page with the basic set of component files that comprise an experience, such as a video file and a metadata file. The EIDR (CUT) or Alt Cut ID column provides the unique ID to use when you deliver the component files.
When you deliver a manifest file for a movie, Google supplements the list of components based on the details contained in the manifest.