When you upgrade your system, you may not want to upgrade your data partitions. For instance when I installed RH8.0 on an old machine, I used ext3, which required a format of the partitions. It is still also possible to screw up a partition table, and that will only affect the one partition, the smaller the better. But the FSH requirements doc, as I read it seemed more concerned about the integrity of the system partitions, which is great for system admins.
