Actually my experience is that GCAA did their part quite efficiently. The problem was that, once the CAAC receives the verification, it's procedure is to then go back to the foreign authority and do their own verification, and THAT can take months.
As to the no accident/disciplinary letter, yes it is Emirates policy to not provide it as the Chinese request, though some individual managers have done so against policy, and you CANNOT begin flying there until this is resolved.
DO NOT start employment in China until you have all the necessary paperwork in place.