[Klaus]

Wim - I use MFT privately. I prefer it over other systems. Yet I do accept the realities and I do not have any issues with them.

If you have any interest in the FACT that the 12-100mm f/4 has a TRUE aperture of f/4 - well, Ok. That's perfectly fine and I do not dispute this at all.
However, for me, that's just a number in EXIF data and something that I choose to achieve a certain DoF in the final image.
That number (to achieve the desired DoF) differs depending on the sensor format. As such the number alone is of no special interest to me - at all.

Within the scope of this discussion, it's DoF and image noise that counts in images - and that's a combination of lens and sensor capabilities.

When I watch a photo, I don't think - oh, that's f/4. I think - that DoF is nice (or not) and the image noise is fine (or disturbing). And I will think of many other aspects, too ... which is why I prefer MFT. ;-)

FACT is that 12mm, 1/100s, ISO 100, f/4, 20mp on MFT gives me the same DoF, FoV, exposure, shutter speed and noise as 24mm, 1/100s, ISO 400, f/8, 20mp on FF.