Nobody has an "agenda" or bias, other than that every single person who ever uses a camera—yourself included—will always have entirely subjective tastes and preferences.
Do try to remember that accusing a company or individual of being paid-off without disclosure is, in fact, illegal. Yes, even if you hide behind a forum username. If you're going to claim someone has been in some way paid-off or otherwise incentivised by one company to make negative remarks about another, you better have actual, presentable proof of your claims. And no, "but they always rate Sony highly!" is not proof of anything. (Other than that Sony do make very, very good cameras.)
Anyway.
This does not surprise me in the slightest, nor should it surprise anybody else who has used these three cameras.
1) Canon and Nikon's bodies are their first generation, while Sony are on their third. Of course Sony are going to have a more well-rounded system; they've had more time to work out the kinks.
2) When it comes to bodies without the context of their lenses, Sony's bodies are the best. Nikon's Z6 feels nicer in the hand but it's still a bought-in Sony sensor with a less efficient CPU, slightly less effective IBIS, only one card slot, etc. And do we really need to spell out all the shortcomings of the EOS R? Nobody is saying it's an outright bad camera, but it doesn't take an expert or genius to spot—let alone use and experience—how much more the other two bodies offer.
3) This is the same thing that happened with the EF mount. The first EF bodies sucked. They were totally, totally awful. Every other camera body at the time was built better and worked better. But the brand-new EF lenses were way ahead of anything anyone else offered, so Canon took over the market, got a massive lead over everyone else, and hasn't been remotely challenged since. (Yes, I know some people like to think Sony are nipping at Canon's heels or have already taken over, but the actual fact of the matter is that Canon lead in global sales by miles.) The same thing goes for RF. Yes, the EOS R body is a mid-level body and not even as fully-featured as other mid-level bodies, and though the sensor is more than capable for most uses, the processor is a little underpowered and so when it comes to benchmarks, other systems will beat the EOS R in IQ. But other systems don't have a 28-70 f/2 or a 50mm f/1.2 (at least not with autofocus), and their "kit" zooms aren't a patch on the RF 24-105, either. No system adapts older lenses as well as the EOS R, either, giving it immediate access to a larger range of lenses than either of the other two systems.
Y'all shouldn't be so precious about the Canon bodies, let alone be throwing out libellous comments. It's absolutely okay to acknowledge that Canon's bodies are very rarely the best bodies of their class/type. Where Canon has always lead is with the lenses, and if you really cared that much about photography you'd know that the lens matters more than the body.
So, yes, when comparing bodies, Sony's absolutely is the best. Nikon's Z6 is flawed but still a very good first try. The EOS R is even more flawed but for a first body for a brand new system it's still acceptably capable. Factor in the native lenses and the EOS R draws even with Sony, in my estimation, with the Z6 behind. Then throw in adapted lens performance and I'd put the EOS R in first, especially if anybody needs really specialist glass like tilt-shifts.
Different strokes for different folks, and no system starts and ends only with the camera bodies.