[Klaus]

Maybe not the best in terms of build quality but optically impressive:

https://www.opticallimits.com/canon_eos_ff/1107-canonrf85f2

[Brightcolours]

" It's also noteworthy that the RF 85mm f/2 STM IS macro is bigger than the EF 85mm f/1.8 USM - confirming once again that mirrorless lenses aren't necessarily smaller than their DSLR counterparts."

You are comparing really old (1992) to new designs here, which means it does not confirm that at all, or it is always confirmed because lenses from the 1960s/70's, for instance, were always smaller (due to the low number of elements) than modern designs.
I dare to say that a modern 85mm f2 for a DSLR with similar sharpness and overal performance will be a bit bigger, because all the elements have to sit a bit further from the sensor due to the mirrorbox, and the number of elements probably would exceed the 9 the EF 85mm f1.8 USM has. So, things are more nuanced than it seems from what you wrote there...

"and the outer discs are almost fully corrected at f/4." Rather, they are not clipped instead of "corrected".

This lens then is quite an attractive offering compared to the old EF 85mm f1.8 USM. The old one has that silent and very fast USM AF over the new one, the new one is sharper, goes down to 1:2 and offers IS. I suspect I'd like to use the new lens due to its unusual background rendering (smooth with weirdness) to get really creative with. But hey, I use a Tamron SP 500mm (1st version) for flower close ups too, that is weird enough on its own.

Thanks for the review, as always.

[Rover]

Is this test on an R5?

[Brightcolours]

Is this test on an R5?

https://www.opticallimits.com/images/8Reviews/lenses/canon_rf85_2/kit.jpg
And "MTF (resolution) at 45 megapixels"


I'd say you have a big chance of that

[toni-a]

Disappointed....was looking for lens to replace both 85f1.8 and 100mm macro, STM and the build quality made it less tempting

[Rover]

Sorry, been reading it in haste between flights.

[Brightcolours]

Disappointed....was looking for  lens to replace both 85f1.8 and 100mm macro,  STM and the build quality made it less tempting

Unless you want it to be weather sealed like L, I would not really care that it extends. While Klaus reports that the inner tube can move a bit when you try, he did not report on any alignment issues. 
The only minus I really see is that it does not have the fastest or most silent AF implementation Canon has.

[Rover]

Anyway, this lens looks like a good gauge of what can be expected from the testing platform, is it not? Just like - say - the Sigma 135/1.8 did for the 5DSR.