I agree that being a SENDCo, one should have the experience top “lead other teaching staff and train and develop them to support children with SEND in the classroom”.
I should be more clear that this was not a question for the average “newby” wishing to go into teaching and jumping straight into being a SENCo.
There are some exceptions that would meet this condition that I can think of. Eg. Teaching internationally and returning to the UK without the QTS, one may wish to focus their many years of experience outside of the country to such a course that would give them the access straight back to being a SENCo here in the UK with the QTS. Also I think there are other very experienced individuals who have been working in companies tutoring or teaching in a capacity and perhaps with a focus on SEN children that might be excellent if given such an opportunity. I agree that it should not be a open option to the vast majority of postgraduates, but I don’t understand why it is near on impossible to follow this track.