The type of requirement need not be just the functional aspect (or customeruser facing requirements) they could also include product andor component requirements.
The product requirements e.g. Supportability, Adaptability and Reliability etc. are characteristics discussed here (as part of the FURPS+ model).
The respective roles of SQC and SQA is the same for all types of requirement (customer and product) with SQC focusing on the 'internal deliverable' and SQA focusing on the process of how the internal deliverable is produced, as per the formal definition.