The only citation can be experience, especially since it's so heavily dependent on the specifics of the situation.
If the refactored mini-function captures something very discrete, like popping an item off of a queue, then of course it's a big win. You'll often ask yourself what the hell the original developer was thinking spilling all these details into an unrelated context.
But if that chunk of code only really makes sense in the context of that function, then moving it into a separate function might not do anything except force future readers to flick back and forth between between the various helper functions and the top-level coordinating function. Have you honestly never had that experience? If so, maybe you're lucky enough to have never worked on a code base containing that mistake.
The only true rule is never to blindly follow rules! Feel free to bear good practices in mind, but always make a new, independent assessment for each situation where you might apply it. For the rule about refactoring into smaller functions, think about whether future readers are indeed going to be able to (confidently) avoid looking at the implementation of those smaller functions, because their meaning is so clear from their signature, or if you're just adding extra navigation and mental work. Sometimes it will go one way, maybe even mostly it will go that way, but sometimes not.
The last paragraph ended up more preachy and patronising than I meant. All I meant was, I've certainly come across code from devs that followed rules too blindly.
If the refactored mini-function captures something very discrete, like popping an item off of a queue, then of course it's a big win. You'll often ask yourself what the hell the original developer was thinking spilling all these details into an unrelated context.
But if that chunk of code only really makes sense in the context of that function, then moving it into a separate function might not do anything except force future readers to flick back and forth between between the various helper functions and the top-level coordinating function. Have you honestly never had that experience? If so, maybe you're lucky enough to have never worked on a code base containing that mistake.
The only true rule is never to blindly follow rules! Feel free to bear good practices in mind, but always make a new, independent assessment for each situation where you might apply it. For the rule about refactoring into smaller functions, think about whether future readers are indeed going to be able to (confidently) avoid looking at the implementation of those smaller functions, because their meaning is so clear from their signature, or if you're just adding extra navigation and mental work. Sometimes it will go one way, maybe even mostly it will go that way, but sometimes not.