Turns out the next generation of the documentation is addressing this. As for why? That goes back in history to before my time. But, note that this option has only a binary state. The option always exists, and must be set to either enabled or disabled. So SnapDrive has to make a choice; and it picked enabled. SnapDrive assumes that if, in the future, NFS/CIFS directories are ever put onto this volume, the new format should be used rather than the old.