I would argue that the 100-500 is another case in point, albeit not quite a stark as the 70-200 and not quite apple-to-apple:But you are referring (at this moment) to super-tele in the EF line, and not the non-existent RF line. As far as RF super-tele, you have absolutely no idea yet what they will weigh.
Then I kindly turn you towards a look at the other RF lenses that are already here. What is lighter than an EF 85mm f/1.2L, EF 50mm f/1.2L, EF 28-70mm f/2.8L? Any of the RF's? No. Sure, the RF 70-200 is lighter than the EF version. Isn't that just about it? The Canon EF 24-70 is 95gr lighter than the RF version. So where is this advantage of RF over EF? I don't see it when it comes to weight, which for some reason, people keep trying to claim.
You claim there is a weight advantage to RF. I don't see it.
EF 100-400 Mk 1 (push pull) 92 x 189 mm 1,365 g
EF 100-400 Mk2 94 x 193 mm 1,570 g
RF 100-500 94 x 207 mm 1,365 g
Adapter Ring add 24mm 130 g
If you are using RF, the EF mk2 lens with adapter weighs 1,700 g and is 217mm long, versus 1,365g and 207mm. Not a huge difference in size but you get 100mm extra focal length (and yes you lose ⅔ of an aperture). The 350g difference is far from trivial. For my usage having a maximum reach of 500mm makes the 1.4x extender superfluous, I need more than 400mm but 500 is OK versus 560mm for the 400mm + 1.4, so one item less in the camera bag.