There are two ways to create an enterprise application:, the first being using the New Application Wizard. Four rulesets will be added to the application, two org-level and two application-level.
The second is saving an existing application to a new ruleset, removing the application-level / work pool / integration rulesets from that application, removing the org-level rulesets from the original application, making the original application built on the new org-level application.
Using the second approach you need to specify a work pool to be able to use the App Explorer in Dev Studio. The PegaSample class would suffice but not as useful as having a Org-specific set of examples.
Since the Org class extends Work-Cover you could modify its Class rule to say that it "is a class group" then define a corresponding Data-Admin-DB-ClassGroup record mirroring what the PegaSample class does.
It would be better, though, to use an OrgSample class for examples, those examples defined in a ruleset other than the Org ruleset. This brings you back to the first approach. Start there creating an OrgSample application then use the second approach to place the Org-level rulesets in a separate Org-level application on which other applications are built.