When you set the lens to say, f11, you can see that the blades have closed to a smaller aperture compared to f2, right? As long as the aperture is physically adjusting to whichever aperture you want, the TTL meter should get the proper exposure.

If you're talking about manual vs auto lenses (not camera bodies), my understanding is that auto lenses stay open to maximum aperture and only close to set aperture when pressing shutter (iow, if you have lens set to f16, lens will stay wide open so image viewfinder will stay bright, and lens will only close to f16 when you hit the shutter). So manual or auto lens, either way, the camera meter should work properly.