Even most of the older post is focused on side-effecting functions. His main concern with the previous approach is that functions relied on outside-the-function context (global or quasi-global state is extremely common in game engines), and a huge source of bugs was that they would be called in a slightly different context than they expected. When functions depend so brittly on reading or even mutating outside state, I can see the advantage to the inline approach, where it's very carefully tracked what is done in which sequence, and what data it reads/changes, instead of allowing any of that to happen in a more "hidden" way in nests of function-call chains. If a function is pure, on the other hand, this kind of thing isn't a concern.