I don't think they are, there's often comments at the top that are posted x minutes ago where x < 10. I don't think posts that new could have that many votes. There's probably a weighting factor comparing votes to recency, maybe other factors too.
Thats my guess as well. Thats why we chose to give it a 48 hour wait, so when the storm has settled, we can pick the top comment.
Scores are available via the API... you should use that.