I hear you that it doesnt make a lot of sense.
That said, I know that even on my 91 318i, a very basic car, I get a not insignificant voltage drop when I turn the car to the "on" position, but not started. This is without any lights, radios, etc turned on.
Why? No idea? It stays there too, its not like it just drops when something is energized and then the draw goes down.
So it is an interesting question...
The test I suppose would be to put a multimeter on the underhood terminals, and let the car sit one time with the CA key nearby, another time with it far, far away. See if it affects the sleep and draw pattern. You should easily see the car wake up, and identify the changes that occur, if and when the CA key comes by, and the differences between what happens if the CA key is left close, or taken far away.
But you shouldnt HAVE to do this of course. Seems like lack of forethought in programming...