That was one point where I wasn't sure quite how to talk about this. In the back of my mind, I have a sense that "gets deflected more" (meaning "longer distance") is actually referring to the same fundamental process that "gets slowed down more" (in the sense of index of refraction: v=c/n) refers to: either way, the time to pass through the medium is longer than it would take to pass through an equally large vacuum region. But I wasn't quite confident enough to phrase it that way in my main reply.