Whether a state is considered to be an independent sovereign nation, or the strength of the nation at that time--given that Afghanistan had just gone through a transition--is irrelevant to the assessment. The assessment is that Canada, the country that has custody of a person, must conduct an individualized assessment of whether each detainee it intends to transfer will face a substantial risk of torture.
Assurances from the receiving state are inadequate because they're unenforceable. Diplomatic assurances are diplomatic promises from high levels of government. The entity in the Afghan government that assigned the MOUs is the ministry of defence. It's unclear whether the NDS considers itself bound by the MOU since no NDS official signed those documents.