Yes, it normally works. If you have formated MorphOS readable partitions here, you should see them.

Be careful - if you use for example old HDD in your external firewire HDD dock, it must have different Disk names and Volume names than your computer disks.

I mounted this way external old MorphOS HDD with DH0: partition and System: volume name ( the same like on system disk) and it isn't work.
DH0 on external disk was visible like DH0.1, so it is OK. But System: volume name produce mismatch and I cannot see the Disk icon and cannot access files.