From Q1A(R2), under the Glossary section, it stated: Container closure system
The sum of packaging components that together contain and protect the dosage form.
This includes primary packaging components and secondary packaging components,
if the latter are intended to provide additional protection to the drug product. A
packaging system is equivalent to a container closure system.
The WHO Stability Guidance provides a bit more verbiage around this, factoring in what your label says about storing in the secondary package. If you were looking for justification of your procedure while conversing with a Regulatory Inspector, this might be a good source.
2.2.4 Container closure system
Stability testing should be conducted on the dosage form packaged in the primary container closure systems proposed for marketing. If the secondary container closure system has protective properties and labelling clearly indicates to store in the primary and secondary packaging (e.g. “store tablets in blisters in the provided cartons”), the secondary packaging may also form part of the packaging system for stability samples. Any available studies carried out on the FPP outside its immediate container or in other packaging materials can form a useful part of the stress testing of the dosage form or can be considered as supporting information, respectively.