We should look at this question in relation to the previous question about the commission of inquiry, which has just been set up by the Office of the United Nations High Commissioner for Human Rights.
The attitude of the current government is not unusual on the world stage. Remember that the same council had set up a commission of inquiry on Syria and a commission of inquiry on Eritrea. Those governments have never bothered to co-operate with the commissions of inquiry. But those commissions of inquiry remained in operation, relying on information from the diaspora and the UN agencies in place for Burundi. So it is not at all impossible for a commission of inquiry to do its work.
Of course, the ideal would be for governments to co-operate. I say this from experience because I was part of an international commission of inquiry on South Sudan. We were fortunate that the government co-operated. We went in, we went out, and we had access to some government services. But even without that, I think it is still possible to come to conclusions that are relevant in the circumstances.