Size of lenses are mostly proportional to the amount of light it lets in (until you go to extreme focal lengths or extreme f-numbers which for most system is somewhere around f/1.2 or below due correction of extreme ray angles in which case they become disproportionately larger).[ “The Micro Four Thirds system is the only mount system that realizes small size, light weight and high image quality at a high level” ]
The keyword in this quote system, which means body and lenses.
It's true that FF bodies are now close in size and weight to M43, but the size of FF lenses cannot be reduced (law of physics).
Just look at the Olympus 40-150mm F2.8 which lets you zoom up to 300mm.
Compare its size to any other brand of zoom lenses 300mm F2.8
And this lenses is super sharp with superb image quality if all you need is 20mp.
(you can google and check all the DXO reports on this lenses).
Hence, what Hiroshi Suzuki say is still true.
Stop plucking numbers out of the sky.There is no doubt that MFT has advantage in 2x crop factor for telephoto.
This is accentuated at long telephoto focal lengths from 400mm onwards to 2000mm.
The problem is that MFT sensor is very small.
Out of the customer base that buy MFT camera bodies, how many buy a long telephoto lens beyond 400mm.
Say for example, 3%.
Now the last known statistic in 2018 or 2019 was that Olympus MFT had 2% world wide market share.
So 3% out of 2% gives 0.0006.
This is the best case scenario.
This is the most optimistic outcome.
The reality may be much worse than that.
How can a camera manufacturing company survive if it plans to concentrate its future efforts on serving 0.0006 of the market.
If long telephoto made all the difference then Nikon P1000 with its 16MP 1/2.3 inch sensor should be the world's top best seller, capturing 80% of the world wide sales. Which did not happen.
JIP and Panasonic are better off aiming at a target market of the masses, with Small, Light, Cheap MFT cameras. Plus Cheap lenses with modest apertures and commonly used focal lengths.