The radiator fan can keep running after you turn the engine off because modern cooling control can command electric fans after key-off. Coolant temperature, air-conditioning load, turbo heat soak and diesel regeneration are contexts that change what that running fan means. How long it runs varies by vehicle.
A brief run can be commanded
The useful distinction is whether the fan run is brief and repeatable, or whether it comes with overheating, warning messages or battery drain.