why would automakers bother to make a mechanism to let the fan run when required?
as for the load part, since you are a technical person, i suggest that you attach a voltmeter to your car battery, start the car. and for a moment, just shut off the fan.
You might notice the engine spin slightly faster, that is because now your alternator is putting less load on the engine.
In winters, you may also experience a longer warm up time.