Im mot so sure I agree with this.
I cant find anything on the net to dispute this either. I believe the 5D4 is a little sister AF system to the 1Dx2 much like the 5D3 and 1DX1 systems were when they were introduced.
All I can do is tell you what I have seen and experienced in the field with myself and others who were shooting in identical conditions
The 5D4 guys were getting A LOT less keepers than I was with the 1Dx2 on our eagle trip. So much so that they were asking me how I had my camera set up.
I had my 7D2 with me and it was set up as close to the 1Dx2 as I could get it
I was very disappointed with the 7D2 results. Extremely disappointed
I Probably had 20-25% less performance and keeper rate. I mean I was shooting in exact conditions and it missed with a much higher degree and frequency as compared to the 1Dx2.
ESPECIALLY BIF'S.- If i could pick it up and track it for a longer distance the 7D2 did just OK where as the 1Dx2 rarely missed a BIF once I had it tracked
The 5D4 guys, 2 of them, both had the same issues. We were shooting in terrible conditions. But they missed right and left
So Im not so sure the 1Dx2 and the 5D4 are the exact systems. I do not think this is a correct statement based on what I have seen with the 3 times I could get both bodies in identical conditions.
Not sure what Canon has done with this 1Dx2 but its a marked improvement over the 1Dx1. I have used both bodies a lot. I have never had a camera this accurate with an AF system. Especially servo use. It Never misses in servo. I have yet to miss a processional shot with the body. The 5D4 that my assistant used missed several processional shots.
So I dont think its the same. I think its a little sister version.
I totally agree with this even applying to the 1DX. I've used the 5D4 and 1dX in exactly the same conditions and have a LOT more keepers with the 1DX. Once it locks in AI Servo it never lets go. I'm so impressed with it and can't even imagine the upgrade to the 1DXII. (But I won't have to imagine for long as I'm upgrading soon!)