I don't know about Duane Paton, but I personally know several birders who use a9ii and a1 bodies with the Sony 200-600mm, and use them for hours at a time without any issues. I also have a pal who uses both a Canon R6 and a Sony a7Riv, so has no axe to grind, and tells me they are both equally easy and comfortable to use.
Another pal of mine bought a secondhand 1Dx, having convinced himself that it was perfect for his needs. He's a big strong lad, but 6 months later he sold it and said it was too heavy to use for more than half an hour. I borrowed his camera a couple of times and found it extremely comfortable for the first few minutes, due to the big grip and wide control placement, but ridiculously heavy, and too cumbersome for regular use.
Personally, I found all my own Canon DSLRs comfortable (50D, 40D, 7D, 7DMkii, 6D, 5DMkiii, 5DSR, 5DMkiv), and I'm extremely pleased with my R5. On the other hand I borrowed an RP from another friend, and found it fiddly and uncomfortable to use with anything bigger than a kit zoom. I also borrowed the original R, and strongly disliked the swipe bar, and found it too easy to nudge accidentally. That swipe bar was almost universally condemned by reviewers and users.
It isn't as back and white as saying brand A has good ergonomics and brand B has bad ergonomics.
It all boils down to individual preferences, which are largely based on how much extended use a person has had with a particular brand or model. Any modern MILC from Canon, Nikon, Sony, Panasonic or OM Systems is capable of stunning photos, and after a short period of adaptation, any photographer should be able to use them intuitively and without discomfort.
Brand loyalty and internet warfare have led to a lot of people "taking sides" and condemning other people's choices, without any experience of the gear they are condemning. A lot of it is stirred up by internet influencers and by people desperate to defend their own purchasing decisions.