I don't think you understand. MFT (or APSC) gives you more reach by increasing pixel density. So you get the "equivalent" of a 600mm, for example. However, if you were to attach an optical 600mm to the same pixel density, you'd have an even further reach (like 900mm or more). In other words, a 100megapixel full frame would offer us the benefit of a super high density sensor PLUS an long focal length.
Olympus will never make lenses like an optical 600/4 for MFT, because it makes no sense to. Those lenses would be exactly the same size as an EF (or RF) 600/4, and anyone buying one would just mount it on a bigger body with a bigger sensor. I mean, why not spend a little more to have a bigger sensor when the relative cost of that is very small compared to the $10,000 lens, and the relative weight/size of the body is immaterial when compared to the big lens. In other words, use a sensor that will take advantage of the smallest image circle possible.
It's totally fair to say, that you're happy with a higher density sensor with a shorter FL lens. But all I'm saying is, this lets us have the higher density sensor with the longer FL lens for super-duper reach, or to use an existing excellent shorter FL length to achieve greater reach. Or, to have more flexibility which whichever lens happens to be mounted.
My concern is that either the deep crop or the reduced image is not as pleasing as, for example, a 1DX with a 600mm and an extender.