It is a model feature that needs its exact manufacturer explanation. It should not be translated automatically into a diagnosis or a promise that one compartment can be serviced independently.
What the observation tells you
Cooling circuits, controls and airflow can be arranged differently. Marketing terms may describe benefits without giving every mechanical detail. A symptom affecting one space therefore still needs assessment against the actual design.
A useful next step
Provide the complete model and the observed pattern. Keep sealed-system findings from any earlier engineer available. This service excludes refrigerant-circuit work, so confirmed technical requirements determine whether the enquiry is suitable.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.