Not sure if this is a defect or just a limitation of the SSJS approach.
1. Click the "New User" button using SSJS option.
2. Fill in the editable fields and click the "Select" button.
3 Click "Cancel" on the picker page. The fields that you filled in are wiped clean when you return to the New User page.
Cancel works as expected in the CSJS approach because the New User page has resetContent="false", as explained in the excellent NotesIn9 video.