The concept of Page Types from a Content Modeling perspective is often confused with the Experience Manager Page Types.
Clients often believe that XPM requires creation of as many Page Prototypes as the Page Types identified in the Content modeling process. This may be misleading cause the 2 don't always match.
Example: we don't want to create a Page Prototype for the Home Page. Editors will not create multiple Home Pages on their websites.
Page Prototypes should be created only for those pages that are commonly re-created by editors and for this reason they are usually a subset of the Page Types.
Different logic applies for Content Types. In this case we probably want to create a Content Prototype for each identified Content Type. However for consistency it would be nice to call "Prototypes" both pages and components.