[Clarification] Doubling of code of requests?

Type of issue: Clarification of architecture

I really like the idea of js-stack-from-scratch and js-stack-boilerplate but I found 1 interesting thing. Why server rendered data differs from client rendered data?

Let's say we want to get list of posts. How do I make requests to API server in old SPA world without SSR? (simplified version)

1. I have an dispatch in componentDidMount, which triggers an actions, which triggers a saga, which makes an API fetch call, so I get the posts. Yahoo!

How do I make requests to API server in new SPA world with SSR?

1. I have an dispatch in componentDidMount, which triggers an actions, which triggers a saga, which makes an API fetch call, so I get the posts. Yahoo!
2. I found such thing as a controller.js which makes the same API call correspond to the component to preload global state. Huh?

Do I misunderstand somewhat? Why do we do it twice? Did you think about it?