Am I correct in thinking that running that command actually accomplished absolutely nothing because of the "incorrect number of parameters?"
Yes.
FWIW I just spent nearly a quarter of an hour digging through
man diskutil and discovered a whole lot of things diskutil can do that I was unaware of including..
- realizing Disk Utility is a GUI offering access to a subset of diskutil of the diskutil verbs
- diskutil can add/change/remove ownership
- the diskutil verb resetUserPermissions has apparently been removed along with any other verb relating to permissions (or at least no longer listed in man diskutil)