I would imagine it is the belief some hold, that continued use of the kill switch will bring about its destruction. Many believe that the switch assembly is marginal at best and not suited for constant use. This belief spans all makes of bikes.Yes, the Tiger1050 cooling fan only runs when the engine is running and the temp is high enough for the fan to be turned on. Also, Mr. T does not recommend shutting off the Tiger using the kill switch except in emergency...I have not yet heard of anyone finding out what problem this causes by continuing to use the kill switch for shutting down the engine.
The decades of experience and design is in favor of the fan running on after shutdown. I have not done a survey but all the cars with an electric fan have that design. At keast I have noticed it on all my cars and I drove rentals for years wen traveling on bidness. I think I mentioned that the bike people might be driven to this design out of consideration for our weak batteries.If the fan runs for a few minutes after shutdown it would lower the temperature of the coolant in the radiator, but given the lack of circulation (engine not running) I wonder how much that would translate to lower head and block temperature.
Not a great deal but it would certainly register. Convection would carry some of the water slowly into the engine but here again I don't think it would do much.
My opinion is we're unlikely to do better than decades of engineering and experience.
I like the idea of running the fan till the rad is cool enuff to shut off the fan. That design would serve to keep the coolant at a more even temperature if it were only a few degrees.Some Numbers to try to see clear.
Fan consumption is just 4A under 12V, say 50W less than lights which are in use during engine start
before ECU on board, fuel injection, every motobike with water cooled had a thermostat fan coupled and no one then to say it's better to stop fan with engine.
At least some cars still work that way.
Engineers do not always work in the customer's interest but above all to respect the specifications and make money !
And they have crossed motivations such as "reliability to start" vs lower coolant a few degrees after shut-off.