DANGER! Beware. After updating my 2013 iMac w/Fusion drive to Mojave, Boot Camp is broken. Instead of the NTFS "BOOTCAMP" volume I now have an APFS "BOOTCAMP_VOL" containing a "bootcamp.dmg" file which appears to be a disk image of my former Boot Camp volume. No idea how to proceed, but be warned if you're upgrading to Mojave.