Actually, this is not what the switch is for and the compatible Pentax cameras had no ability to set the aperture. The "Auto" refers to auto diaphram stopdown and not to any auto exposure function.
Super Takumar are auto-diaphram lenses, as are almost all modern lenses though the feature was somewhat new at the time these were introduced. When using the lens on a thread mount Pentax body and with the switch is in the Auto position, the aperture remains at maximum regardless of the f/stop ring setting until the camera is fired and it presses a small pin on the back which closes the aperture to the chosen f/stop. The Manual switch position is used to close the aperture to the chosen setting in situations where an accessory is used that disconnects the body from the lens (e.g. bellows, extension tubes,...) or when you wish to view at the chosen working aperture (DOF preview).
When you use the lens on an m4/3 body with an adapter one of two things happen. The adapter may push the pin all the time. If so, the lens closes to the chosen aperture regardless of the position of the switch. If the adapter doesn't push the pin then you need to set the switch in the Manual position when shooting in order to use any f/stop other than maximum..
The switch would be useful to allow critical focus wide-open, and then set the switch to stop down the lens. This assumes the adapter does not push the pin in. If I get an M42 mount adapter, I would make use of the feature on the lens.