A temperature control may belong to washing rather than offering a freely adjustable drying temperature. Programme functions vary, so the button's effect should be checked in the manual.
Understanding this situation
A disabled wash-temperature choice during dry-only is not necessarily a control fault. The drying programme may instead offer fabric selection, duration or a target finish, each with its own limitations.
A useful next step
Use the documented controls for the chosen drying mode. Do not switch to an unsuitable fabric programme just to obtain a different displayed number. Report a restriction only when the model's instructions confirm that the requested setting should be available.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.