He's not talking about eager loading associations. It's AR 3.0 backed by arel that allows ALL queries to be lazily loaded, as in, they are declared in the controller cleanly, but they only run in the view (and furthermore they only run if the view needs them).
Including assocations is an orthogonal issue. As far as I know they get the same benefit out of the box in Rails 3. For example, I think you can say:
@posts = Post.where(:published => true).include(:comments)
And it will still load it all eagerly, but it won't do it until you actually iterate over @posts.