in the routing refactoring we did together with crell from drupal, we split those route enhancers out of the dynamicrouter and made them more generic. i think the documentation above is just fine as is (there was no BC break, and we need not confuse people with those details).

however maybe we could add a paragraph here to mention that users can use the enhancers to their own means or write own enhancers to do all kind of things with the route defaults. (not limited to controller and template anymore)