SQL Server Facets: "Linked Server" exist but "Registered Server" doesn't - why? I'd like to monitor multiple SQL Server instances.
Something similar to what is described in "Monitor Your SQL Server Linked Server Configurations with Policy Based Management" but instead of using "Linked Servers" facet to employ a "Registered Servers" one.  

But there is no "Registered Server" facet.
Why? I'd like to grasp this absence from conceptual p.o.v.?
and how to make the same as described in the cited article using registered instead of "linked" servers?

SQL Server 2012 R2, Windows Server 2008 R2
There is no such thing as a registered server in SQL Server itself.  

Registered Servers can be added into SQL Server Management Studio to simplify managing multiple servers.  

Policy Based Management, and facets, cannot be used against Registered Servers since they don't actually exist in the database engine.