To progress from Crew to Watch Manager and Station to Group Manager, there are in-band processes. These supplement the ADC levels of management. Some services are using just an interview to promote in band, others use job related tests and assessments.
Job related tests should test technical and practical knowledge that is expected of the level of management. For example, I have recently been assessed using a written exam for the technical knowlede, a presentation of demographic information and an incident command assessment commensurate with Watch Manager B.
The old style exams, which I have passed were a test of memory and demonstration of one's ability to to oversee a standard drill and small incident aswell as deliver a debrief.
ADC's are aimed at testing management skills. As a manager, you are expected to manage.
There are problems with the ADC process, but it appears that theses may be caused by a lack of understanding both of those taking them and those assessing. It's all new and shiny and will take some time to bed in, but it also relies on peoples ability to adapt to the new processes and leave the past exams behind, even though it does grind that all that time and effort has now been for what appears to be nothing.
In financial terms it is impossible to have an ADC at each level and once on development, it's up to you to gather evidence to support a claim that you are competent against the role maps.
Post dispute, all existing managers were deemed competent for pay purposes only, so who's to say that assesments for competence won't be introduced for managers?
