mankan - it wouldn't be beyond the realms of possibility that someone had to drop out of the interview, and your partner was actually an employee posing as a difficult partner - just a thought.
From what I can gather, they're looking for how you respond to an individual like that, do you prompt them, did you pick them up when they didn't do a brief for the approach, did you remind them of the before landing checklist? etc etc etc
If my partner were to begin the approach without a briefing I would be speaking up.
Just my $0.02
ES