On adding support for new mime types becoming more complex in 3.1

I am adding support for a new mime type in a rails 3.1.0 rc5 application and noticed differences between 3.0 and 3.1 that are detailed here:


There you can see that in 3.1 you need to do an additional step to add global support for rendering to a new mime type. Can anyone tell if the added complexity is intentional or not? I think it would be more intuitive if ActionController::Renderers.add was the only thing required like in 3.0.