Leave it installed unless the engineer has specifically arranged otherwise. Removal involves a supported mounting, water connections and an electrical supply, so it is not a helpful general preparation step.
What the observation tells you
Taking the unit down can erase evidence of the original leak route or alignment and create a second problem at the sink. It may also be heavier or less securely supported than expected. Do not loosen the mounting to make inspection easier.
A useful next step
Prepare safe access and provide photographs instead. Tell the engineer if another person has already disconnected anything so the visit can account for the changed condition.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.