SUMMARY
When moving multiple files between different drives, failure part-way through results in neither the source or destination containing all files being transferred, which can be equivalent to loss of data for complex directory structures. In cases where you are moving files between different drives, "move" could wait until the whole transfer is complete before deleting the source files. 

This is equivalent to a copy-paste, then manually deleting the source. You could do this manually, but when I had this issue and needed to use a backup to restore my data, I just didn't know it would behave this way. I believe MacOS will wait until the transfer is complete before deleting the source so that is likely what set my expectations.

STEPS TO REPRODUCE
1. Click and drag to Move multiple files from one physical drive to another
2. Cancel transfer part-way through

OBSERVED RESULT
Transfer remains in part-complete state, with some files remaining at the source, and some at the destination, with no complete version available anywhere.

EXPECTED RESULT
Reverts to a state before the operation was initiated, since the transfer is happening between different drives and won't use up any additional or unexpected storage as files are duplicated.

SOFTWARE/OS VERSIONS
Operating System: NixOS 24.11
KDE Plasma Version: 6.1.4
KDE Frameworks Version: 6.5.0
Qt Version: 6.7.2
Kernel Version: 6.8.9 (64-bit)
Graphics Platform: Wayland