There are no magic answers to give in the interview that make one or other outcome certain. But it's the interview itself that leads to the outcome - if the evidence checked beforehand was not all satisfactory, the application wouldn't get to the interview stage.
Anyone without a job offer, applying under SMC, is going to get interviewed by the CO, and the interview is to let the CO evaluate their knowledge of NZ, preparedness to settle into NZ life, and therefore, critically, their EMPLOYABILITY. Here's a link to the official list of requirements.
http://www.immigration.govt.nz/opsmanual/i43652.htm
If they look well prepared, so an employer is likely to get a good impression when they apply for a job, the applicant will get Residence. If the CO has their doubts, then that is when the SMC JSV is offered - we say, brutally, it's the 'we don't think you can do it, but here's one chance to prove us wrong' visa.