A conversational final round can be completely normal, especially with partners or senior interviewers. They often use the case as a platform to explore judgment rather than follow a rigid script.

A relaxed tone can indicate rapport, but it is not reliable enough to predict the outcome. Senior interviewers vary widely in style.

Judge your performance by the quality of the discussion, your reasoning, and how you handled challenge. If useful, this guide on final-round consulting interviews gives more detail.

partner round was basically a conversation for me too.

friendly is nice but I wouldn't use it to predict result.

R2 style varies a ton by interviewer.