Both the 600 and 800 f/11 use DO elements (albeit not hyped at all). DO is clearly cheaper to implement at this point than fluorite, so very likely it will have DO. Fluorite is being used sparingly these days. My EF 800 f/5.6 has a fluorite front element (huge) with clear glass protection in front. The RF 800 f/5.6 has the fluorite elements moved to the back (much smaller) and it is not quite as good (particularly with extenders). A BR (Blue Spectrum Refractive) element (as used in the RF 85mm f/1.2 is another possibility for CA correction.
I hear what you are saying, however some of the RF version are a weird parts bin special.
All of the EF mkIII super whites aren't quite as good as the mkII's are from an optical point of view. But the mk III's have better balance due to the re-arrangement of the internal elements, moving the heavier elements further into the lens shell, making a better balanced and light lens.
The EF 600 f4 II L and mk III have two flourite elements and the only ones that I amaware of that do. The RF versions are pretty much the EF versions with an integrated EF to RF adapter. The RF 400mm F2.8 LIS and RF 600mm F4 LIS are in fact re-worked EF mk III versions. So they are optically slightly worse then their EF mkII cousins, but balnce better and are a lot lighter.
The current RF teleconverters are slightly worse than the mkIII EF versions optically.
The current RF 800mm f5.6 is a parts bin "special" using a EF 400 III LIS with a custom integrated 2x TC and the filter holder placed after the TC group. Weirdly, the EF 400 f2.8 mkII and a mkIII TC is actually slightly superior than the native RF version...go figure. The same is true for the new RF 1200mm f8, it's a EF 600 f4 mk III mated to a custom 2x TC with an integrated EF to RF adapter. Similarly, the EF 600mm f4 mkII with a 2xTC mkIII and an adapter is slightly superior optically than the parts bin / Cobbled together RF 1200mm LIS.
