Really? That's confusing!
From wapbl(4):
WAPBL requires the super block to be in the UFS2 format. The super block
format can be checked using the -s option with dumpfs(8), and older FFSv1
file systems will need to be updated to the newer super block layout with
the -c option to fsck_ffs(8).
So, there is such a thing as a FFSv1 with a super block in UFS2 format?
From this description, I was under the impression that updating the file
system's super block layout _IS_ converting it to FFSv2.
Could someone please explain the difference between a FFSv2 and an
FFSv1-with-UFS2 superblock, and what advantages FFSv2 has over this?
A friendly pointer to relevant documentation would of course be very
welcome too.