[chongli]

But I'm referring to the cognitive overload incurred when you try to optimize it, thinking about list creation costs, then stream fusion to avoid it

That's not true. This article is about a library that works as a drop-in replacement of the default list processing functions in the Prelude. Eventually, it may be possible that these functions will be put into the Prelude itself. This would allow naive users to get all the performance gains from stream fusion without ever knowing it's happening. All of the "cognitive overload" is taken care of by the researchers who developed this technique and the library authors who implement it.