Hi Yasko!
Sorry, but your arguments have already been disproved:
When you take a look at the recent Canon RF patents you can see that even tele zooms can be made a little bit smaller, although this was not expected.
When you think about standard FL, WA, and UWA here we had a lot of discussions in this forum that those lenses could be built smaller than their EF equivalent because of the smaller backfocus distance possible.
Of course, if Canon decides to make a more complex optical formula ir if they add macro functionality like at the RF 35 this could make a bigger again.
And if you compare this Canon RF 35mm f/1.8 IS Macro STM with the EF 35mm f/2 IS USM you can find this:
size (diameter x length):
74,4 x 62,8 mm vs. 77,9 x 62,6
So the RF lens has the same length and slightly smaller diameter ALTHOUGH macro feature was included AND the aperture got slightly wider.
So shallower DOF and less ISO in the same package.
Ans as icing on top the IQ / sharpnes and CA have been improved over the already very good EF lens:
https://www.the-digital-picture.com...4&Sample=0&CameraComp=453&FLIComp=0&APIComp=0
So that would be my German
rule-of-thumb.