Comment # 20 on bug 1218864 from Giacomo Comes

More info.
The "corrupted partition", that is the one that causes the message
"not a correct XFS inode" to be generated when it is booted from,
can be mounted with groub2-mount without issue.
I manage to enable debug with the command:
  grub2-editenv - set debug=xfs
then booted and recorded the boot process.
I have a 2:15 22MB video of the boot process. If interested, please let me know
how to make it available to you.
In such video it is possible to see:
  fs/xfs.c:1010:xfs: Reading sb
  fs/xfs.c:288:xfs: Validating superblock
  fs/xfs.c:300:xfs: XFS v5 superblock detected
  fs/xfs.c:1042:xfs: Reading root ino 128
  fs/xfs.c:533:xfs: reading inode (128) - 128, 0
and then more inodes are read until you see the following:
  fs/xfs.c:533:xfs: Reading inode (0) - 0, 0
  error: ../../grub-core/fs/xfs.c:541:not a correct XFS inode.

Later in the boot process you can also see:
  fs/xfs.c:533:xfs: Reading inode (25942926) - 16491888, 3072
  fs/xfs.c:533:xfs: Reading inode (25942927) - 16491888, 3584
  fs/xfs.c:533:xfs: Reading inode (197568495624) - 123371593736, 0
  error: ../../grub-core/kern/disk_common.c:26:attempt to read or write outside
of partition.

So it looks like the code that decides which inode to read next have some
glitches.