Make a decision
Photographic proof versus operating proof
One scope
Photos can establish visible condition at identifiable access points.
The other scope
Operating proof documents startup, airflow, drain function and relevant safety checks.
A concrete example
A wheel photograph can show removed buildup; it cannot show that the motor runs without vibration. An operating check can show function; it cannot show the hidden branch was cleaned.
Which question settles it?
Ask for both where appropriate; neither form of evidence answers every question by itself.