I don't know much about this issue, but just a shot in the dark: Apple is using a new technology called Core Storage that's "layered between the whole-disk part

I don't know much about this issue, but just a shot in the dark: Apple is using a new technology called Core Storage that's "layered between the whole-disk partition scheme and the file system used for a specific partition" in order to manage FileVault and their fusion drives. It's also apparently a technology that's in flux, as there are certain incompatibilities in regards to fusion drives (possibly custom created ones?) with the release of Mavericks. John Siracusa mentioned this in a recent podcast, and even hypothesized about how Core Storage might be a stop-gap between HFS+ and a new Apple-designed file system. Could it have something to do with this?