Yesterday there was a lot of discussion (internally) around Servers vs. Services and how to classify types. The result is that it's still something of a vague semantic. In general, plugin developers tend to declare a type a Server when it is backed by a discoverable process, regardless of the parent type. For example, an RHQ Agent is a server as it is a discoverable process, but so is the Agent's JVM. The difference is that the Agent is available as a "Top Level Import", meaning its parent is the platform and it must be explicitly imported into inventory. The Agent's JVM is not. Its parent is the Agent resource and it will be imported automatically.
But they are both server category resource types. The issue is that Inventory->Servers can present a confusing resource list as it shows all servers, and there can be several for one "top level import". It's unlikely that there will be any change to the categories offered. And type categorization will continue to be loosely defined and left to the plugin developer.
So, I added a new Inventory option, currently named "Inventory->Servers - Top Level Imports" to present a list of only servers that have platforms as parents. In essence, the servers that the user chose to import, and not their sub-server resources.
Try it out and let us know if it's useful, confusing, or should in some way be improved.
Also remember to love your search bar. Saved Searches are powerful and can get you to a specific resource list better than the generic options on the left hand side. Another enhancement may be to make the saved searches available in the LHS. Not sure how easy that may be to do...