Quality should increase train wagons capacity.

[mmmPI]

The math are wrong, following your reasonning the throughput of a rail is directly proportionnal to the carrying capacity of a train, so if you were trying to make the longest train possible for whatever reason , attempting to play smart or something , then you would have to conclude that the rail has an infinite throughput. If your train could carry 8 billion coal, ( just scale loco and wagon accordingly) then it would carry 800 000 000 000 tile coal/s you can divide by 25 and 50, it will yield a gigantic number that is not more correct than the 640 coal/s unfortunatly.

You are forgetting that math, as a language, purely focuses on abstraction and is only a tool to describe reality, not answer.

We can all agree that proportions per wagon and math isn’t mathing. And trains aren't worth investing in at the endgame. In reality, you send a few-kilometer-long trains because it’s the most optimal approach, and in the current in-game state, even this approach isn’t even worth considering.

Your math were wrong and i believe fairly obviously, if you have something you think is incorrect in the graph i proposed please feel free to explain.