That data would only be relevant if the exact same players did both.
All that says is that worse players do 10m, which makes sense.
For example this.
https://paragon.fi/node/589.html
The same people who did 25m first and 10m first go boss to boss and describe the difference.
That is for firelands tho but its basically the same argument being made here.
More space.
Less damage from boss abilities.
Far less health in comparison to the players.
Which is why they even said 10m was easier.