This will not include b.a.foo in the resulting document for C, even though we would think so (since the @IndexedEmbedded in C doesn't mention any restriction on what to embed).
The reason is, we only take into account the top-level "includePaths", and if it's empty, we interpret that as "don't include anything" in embedded entities...
The issue can be worked around by specifying explicitly the paths to include on C.b.
Note that this issue is here since 5.5.0.Final at least (I didn't check previous versions).
Another issue is that we don't prevent upper-level restrictions to be broader than nested restrictions. For instance:
This will include b.a.bar in the resulting document for C, even though a.bar is not part of the document for B.
Moving the "broadening include paths" issue to as a follow-up ticket.