Yeah, in Inception's case, I thought the exposition was done fairly well. Ellen Page seemed remarkably capable/unquestioning of the the concepts behind everything, but then I just assumed that was because it was set in some near future where that kind of technology isn't so "!!!". So that lack of explanation right there is an example of what Chair wanted more of. Letting the audience work stuff out.
And frankly, I think without explanation, it would come off very badly. People would just be like "Why is Limbo there? Why can't they go into more dreams? Why can't they dream up dragons and monsters and stuff?".
The explanations were done fine.