I think you kinda missed the point. The point is that trying to make a user-friendly API with the familiar, highly composable, and extremely common io.Reader th

I think you kinda missed the point. The point is that trying to make a user-friendly API with the familiar, highly composable, and extremely common io.Reader that everything (including Go's stdlib) encourages you to use ends up putting you in this unfortunate design corner if you also care about performance. It's frustration about getting close to a good API, but not having any reasonable way to close the final gap, forcing you do you to [do] stuff like you mentioned: have multiple near-identical APIs for performance, and needing your users to understand and use them correctly to get a good result.