When interviewers say "nice job" on the case, do they actually mean that?

I had a final round interview with a senior-level staff member recently, and he challenged some of my frameworks and strategy somewhat intensely. I'd say most of the time, I'd explain why I was doing something after he challenged it and he agreed and softened his demeanor. Sometimes, however, I had to revise my approach based on what he stated, and I usually was able to go in the right direction. I felt he was kind of being a douche at times because I've never really had someone like that before for the most part.

He ended with "nice job" on the case, and so like, is that sincere? Or is it just said to be nice?