Please note that this is for 2012.10.06, which doesn't appear to be an option.

genfstab, when run without parameters, gives "usage: genfstab root [options]". If, however, you run "genfstab /mnt -U" or "genfstab /mnt -L" (I can't speak to "-p"), it gives an fstab based on device names, not UUIDs or labels as expected.

Either the help message should read "usage: genfstab [options] root" or the utility should properly parse options given at the end of the parameter array.