Here's some info from Ars Technica:
The new partition is actually considered a different type:
Apple_Boot
. The Recovery HD volume won't be automatically mounted upon boot and therefore won't appear in the Finder. It's not even visible in the Disk Utility application, appearing only as a tiny blank space in the partition map for the disk. But as shown above, the command-line
diskutil
program can see it. Diskutil can
mount it too.
Apparently Apple has decided that the ability to boot a Mac into a known-good (software) state is well worth sacrificing a small amount of disk space. MacBook Air owners or other Mac users with diminutive solid-state disk drives may disagree, however. In that case, the disk space can be reclaimed by some judicious repartitioning with Disk Utility (or the
diskutil
command-line tool) while booted from another disk. But don't be surprised when the fellow at the Genius Bar frowns a little at your deviation from the Apple Way.