I also did the french MMI and the McGill one in this cycle and at several times (at both occasions), they told me that their questions were over. However, most of the times, the interview ran off time some seconds later.
But in one station at McGill, I clearly completed all the questions, and the interviewer tried to invent some new ones to pass the time left.
I think that it doesn't really matter if you produce long answers or small ones, the key is really to use logical and clear arguments.
In my case, I answer pretty quickly to the french MEM, and I got a score in the top 5 %, so whatever the type of interviewee you are, just be clear and logical and everything will be fine !