No, you're not really missing anything
RFC 66 provides support for both shared library WARs and share services WARs, i.e. RFC 66 will turn a WAR file into a bundle which can import packages (shared library) and services (shared services) from other bundles.
The migration path used to be WAR -> shared library WAR -> shared service WAR -> dm Server Web module. It's now become WAR -> shared library WAR -> shared service WAR with the shared library and shared service WAR support being provided by the RFC 66 reference implementation. The best way to think of a Web bundle is as an umbrella term for both shared library and shared service WAR files.
We've updated the programmer guide recently to describe some of these changes, and the dm Server extensions to the RFC 66 RI. Until dm Server M3 is released, you'll have to download a nightly build to get the latest documentation. If things aren't clear from the docs, please let us know so that we can update them.