In other words, on a Super Takumar lens or Takumar lens, there is a connection with the meter switch and the meter electronics on a Spotmatic F. Soon as you put an SMCT lens on, the meter switch is disconnected and the meter is always on.
You don't have to disassemble the camera to discover this. Just take off the lens and slide the aperture cam (inside top of lens mount).
The meter is only accurate with Super Takumar or Takumar lenses when Depth of Field Preview switch is up. The meter is only accurate with SMCT lenses when Depth of Field Preview switch is down.
With Super Takumar or Takumar lenses, you can use the Manual / Auto slider on the base of the lens as you wish. With SMCT lenses a tiny pin enforces the fact that you must always keep this slider on Auto. If you override this tiny pin and leave the SMCT slider on Manual, you will double-compensate for aperture and the metering will be far-off. (How can this happen you ask? If you also shoot a regular Spotmatic and interchange lenses you might leave a lens on Manual - it's happened to me).