I see.  The original way seems omit the optional Id, only leave the label field in list. Maybe that is the reason why i can pass the test. So both of the way can make it works, obviously, your way is more pro and regular. Thanks.
Refer to the doc of YaST team(YCP version), recorded both methods:
http://doc.opensuse.org/projects/YaST/openSUSE11.3/tdg/ComboBox.html