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:

http://www.engineyard.com/blog/2010/render-options-in-rails-3/#comment-165480156

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.