The electric fan coming on after the car is shut off is a good thing.

After the engine is shutoff, the temperature underhood continues to climb and depending what where you are taking measurements, will peak 15 - 25 minutes later. This ages non-metallic parts much faster.

With a mechanical fan, there is no airflow after the engine stops, thus higher temperatures will be reached during a hot soak.

Now, if the electric fan is not sufficiently sized, or is being used in parallel and causes a restriction, then better off without.