As long as you work exclusively with direct disk paths, yes, that is the extent of the damage you can do.
The real issue that can lose data occurs when you mix /mnt/user paths with direct disk paths, where the exact same physical file shows up in two paths, so moving a file can result in the OS erasing the content of that file.
Normally we tell people to avoid disk shares and work exclusively with user shares, but you want to do multiple disk copies at once, so disk to disk is easier to deal with, and as long as you understand how to make user shares by creating root disk folders you should be fine.
You can view and read your user shares over the network during this process so you see how things act. Any root disk folder automatically becomes a user share with default public access. You can update that however you wish in the GUI on the shares tab.