Hello,
Please see attached screenshots (Windows 10 Enterprise Edition x64, latest TP build). Two projects make use of the same shared DLL. After running both setups, the shared counter for the file SBKERNEL.DLL is "2". After uninstalling one project, the shared counter is "1" and the file is still there. If it is "0" then the uninstaller removes the registry key and the file.
Does this help?
Friedrich