Depends. If the answer was posted within few seconds(in your case, it was within 10 minutes) it's completely up to the OP to delete it, or have it remain with information which will make it better than the one posted.
I don't see how this is a problem unless it's something like the same answer copy+pasted over an hour or so later. I wasn't the one who handled your flag, but I'd have marked it invalid if you asked me to remove the post.