There is a fundamental flaw in the way BIM 360 Docs and Desktop connector manages file editing by a basic lock. I believe that Plant 3D and maybe Revit have this figured out properly, and I can't really speak for Revit.
It is good to be able to lock a file to prevent someone adding a version while I am working on it. But if they have opened it, while I am working on it, and made changes as well. If I save the file and it is synced to BIM 360, then the lock is remove lock is removed. There is nothing preventing the other user form saving their work over mine.
In a checkout system like in Plant 3D unless a user 'checks out a file the user receives a copy that is a read-only version, set in the file meta data properties. The same workflow could work in BIM 360 as the locking feature. The only required difference is that a file living in BIM 360 has the metadata set to read only unless it is checked-out in which case it should be locked to the user. Anyone else who downloads a copy of the file should be able to but it should still be marked Read only.
Current situation Example:
User A: Opens a drawing (BIM 360) in Civil 3D. BIM 360 Locks the file.
User B: Open the same drawing in AutoCAD (no prompt or warning given). At this point if this user saves any changes (they can make changes) BIM 360 will reject them because the file is locked.
User A: Saves and closes the file. Changes are synced and BIM 360 removes the lock.
User B: Now saves their changes. The drawing is synced and their changes overwrite the previous version effectively removing the changes User A has made.
Recommended situation Example:
User A: Opens a drawing (BIM 360) in Civil 3D. BIM 360 checks out the file to that user (same as the current locking feature), and removed the read-only property on their copy of the file (part of the download and sync procedure).
User B: Opens the same drawing in AutoCAD. The file is downloaded or synced as a read only, therefore AutoCAD prompts the user that it is a read-only drawing. The user is prevented from making changes locally as well as in BIM 360.
User A: Saves and closes the file. Changes are synced and BIM 360 removes the check-out (a.k.a. File check-in). The local file is marked read only and BIM 360 is updated.
User B: Has no changes to be saved because the file was read only. Design time loss saved.
Similar posts that appears to be not getting any attention:
Set autocad file Read Only when editing
https://forums.autodesk.com/t5/bim-360-ideas/set-autocad-file-read-only-when-editing/idc-p/10448810#...
Only unlock files manualy
https://forums.autodesk.com/t5/bim-360-ideas/only-unlock-files-manualy/idc-p/10448811#M14618
Vault Behavior for Desktop Connector
https://forums.autodesk.com/t5/bim-360-ideas/vault-behavior-for-desktop-connector/idc-p/10448813#M14...