He also shows the slight advantage of the Nikon D850 over the a7R III, which comes in at 13.7 EV vs. to high ISO performance (we have comparisons coming showing parity between high ISO a7R III and a9 performance).
Now, Sony, if you could please offer us visually lossless compressed Raw so we don't have to deal with 80MB files (and longer write times and fewer images per card) for no reason, I'm sure we would all be happy... The a7R III, like many Sony predecessors, has a separate higher conversion gain (HCG) circuit at the pixel.
See our 8MP, or 'Print' normalized, dynamic range figures below.
These are more comparable to what DXO might report, for the benefit of your own comparative efforts (blue: a7R III | red: a7R II): You can see the Sony a7R III encroaching on the ~15 EV rating of the Nikon D850 at ISO 64, but achieved at ISO 100 on the Sony, thanks to lower read noise.
It's worth noting our a7R II figures are higher than DXO's published 12.69 EV (13.9 EV 'Print') figures, possibly because they tested an older unit prior to uncompressed Raw and improvements to Sony's compression curve.
See our table below, which also compares the a7R III to the full-frame chart-topping Nikon D850, ranking based on highest performer: While the Nikon D850 is the top performer here, its important to note that this is only the case if you can give the D850 the extra ~2/3 EV light it needs at ISO 64 (which you often can if you're shooting bright light or a landscape photographer on a tripod).
That's what allows one to get unbelievably crisp, 'medium format-like' like files from a Nikon D810 (try zooming into 100% on that linked image and tell us you're not impressed). While in some circumstances the Nikon D810/D850, or medium format, may afford you slightly cleaner more malleable files, the a7R III takes a significant step at closing the gap.