Launch "Printer Setup Utility" from terminal
If you examine using ps the command launched by Printer Setup or when adding a printer through System Preferences, you'll note that it includes a -psn qualifier that directs the application as to the "process serial number" to use to communicate with the application. This effectively tells it how to connect and launch the windows necessary for the calling user/process and it's used for identifying various processes and instances of executables. 

Unfortunately its unclear how -- or even if -- you'd actually use this to launch from the command line as its usage is normally invoked from within another calling application using system calls and it seems to imply that you need to create certain "Process Identification Constraints" as part of the call out. 

Much of this seems to be marked up in Apple's online documentation as being Deprecated in OS X v10.9 so I'm not sure what to make of this or how to direct you for using it as Apple seems to be advising against the sorts of systems calls that utilize it moving forward. I'd expect to see the sort of calling mechanisms going away in future versions of OS X. 

Further information is available at:

https://developer.apple.com/legacy/library/documentation/Carbon/Reference/Process_Manager/Reference/reference.html

and 

https://developer.apple.com/legacy/library/documentation/Carbon/Reference/Process_Manager/Reference/reference.html#//apple_ref/doc/constant_group/Process_Identification_Constants

While I realize this doesn't resolve your issue, it does explain the behavior your observing and the reason why you're not getting the expected UI launching.