Getting an interview means somebody on the adcom thought, at least, you might maybe be an ok addition to their school.
It doesn't mean your interviewer thought that. They may not be the person who wanted you to come interview. The person (or people) who first saw the file and hit the invite button may be the only people on a 20+ person committee who wanted to give you a chance, and if your interviewer didn't agree with their decision to invite you...
Compound this with schools often interviewing 10x as many candidates as they have spots, your status as Canadian, stats problems, some schools not considering the whole file before inviting you, and perhaps not being the best candidate your interviewer has ever seen walk through the door...
I know it sucks, but you can see how the puzzle fits together, right?
^ Correct
Post interview, they're looking for any reason to narrow down a whole bunch of qualified individuals.