Who knows, I didn't design the sensor or produce the chart, point being I was expecting the a7r4 in crop to be a lot better than it is, I find it very disappointing in fact that with bsi and the amount of research and investment Sony has poured into FF how far they have got, not very!
I must admit that I don't spend enough time on here to know where the ISO-invariance comparison tool is ;-)
I'm not sure how useful it is in the real world - I mean, who shoots an image 5-6x underexposed anyway...
Maybe this would be more meaningful:
Neither of these comparisons tell anything like 'the full story', only that output from one camera can be judged to be better or worse depending on the parameters you choose to impose.
The standout feature of these, to my eye at least as a largely impartial observer with no want or need to own either of the cameras in question, is that the output from the A6600 does appear to have either an AA filter (already dismissed earlier in the thread) or some kind of noise reduction employed.
In any case, you are clearly very happy with your A6600, which is great! I'm confused why you would feel the need to make such comparisons and also why you seem to be suggesting that developments in sensor tech within the same company are somehow divided between FF and crop sensors in isolation?