The spec states:

A library jar, EJB jar, application client jar or rar archive is a bean archive if it has a file named beans.xml in the META-INF directory.
...
In an application deployed as an ear, the container searches every bean archive bundled with or referenced by the ear, including bean archives bundled with or referenced by wars and EJB jars contained in the ear. The bean archives might be library jars, EJB jars, rars or war WEB-INF/classes directories.

I wonder if the intention wasn't to support jars packaged inside RAR instead of the whole RAR. Though I'm not sure about RAR packaging structure.