Current status: open, not assigned
This is a FoafVocab issue, documented as such by linking it from the IssueTracker page.
From the current term definition for foaf:Document:
We do not (currently) distinguish precisely between physical and electronic documents, or between copies of a work and the abstraction those copies embody. The relationship between documents and their byte-stream representation needs clarification (see foaf:sha1 for related issues).
The missing disinction between physical and eletronic documents makes expectations hard to meet.
When an issue is resolved or its status w.r.t. the FOAF spec changes, that changed state of affairs should be documented somewhere less transient than the wiki. See IssueTracker for more notes on issue management conventions.