I probably should re-emphasize "to use on safari..." as the circumstance for that statement. Not to appear contradictory, but in other situations, the light weight and extreme range make this 600mm (or 800mm) lens the preferred lens. On a safari, weight really isn't a big issue but flexibility in zoom range is extremely important. When you are carrying your own equipment on your back, weight is a consideration, and, for wildlife, which is mostly "observe-from-a-distance" photography (as johnmoyer points out from his images) the wildlife is most likely not going to be coming your way - unless they are charging you for invading their space, in which case, it doesn't matter what kind of equipment you have as you're running as fast as you can away... 😉 - and will not let you get to close to them. For bald eagles, for example, getting shots of them feeding on the shore or resting up in the trees, 100m is about as close as you'll get as they have an innate sense of when you get "too close" and will take off.
To your point about the new RF200-800, this is a nice addition, depending on, as I think we've all agreed, on what situation you'll be using it in... It's a big, heavy monster, and while that might not be a factor in, say, a safari, carrying it around in a backpack all day might be. Also, on safari, I think a minimum 200mm would not work in many circumstances as that would often be "too close". 
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