Don't worry too much about it. Some people get invited to ad some don't, it just depends whether they feel like they know enough about you.
Some people get Interview and ad invite at the same time, others the ad invite later, others no ad invite
If your interviewer was asking you about yourpost MBA plans its most likely cause they felt you weren't clear about those in your application
As per their words: they look for reasons to accept you, not reasons to reject you
Posted from my mobile device