ETA: Oh, yes. I see now that Pages is mentioned.
Hmm.
I'm undecided on whether this is actual breakage or not; I've come to notice (especially from using things like VMS) is the UNIX mantras of "everything's a file" and "everything's plain text" are a bit simple for the real world.
I'm unclear, though, on the benefits of structuring documents in this way. Surely if there's lots of metadata and wotnot to maintain, some kind of container file à la OpenOffice.org would be in order?