I suspect it's using a camera sync profile rather than a disk mode type of profile.
There are still digital cameras out there that appear specifically as cameras, using a different transfer protocol, rather than just showing up as a disk drive.
Photo transfer from the iPod (ie, photos loaded in with the camera connector) worked much the same way, except that of course the iPod did show up as an external drive in the process (photos were read from the DCIM directory).
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