They are both mostly right but the devil is in the details and to try to not get too dogmatic about things. For example function length is one of those things that you can obsess about and debate endlessly.
What's the value of extracting a function that is used only once or twice. It's probably very limited. It's debatable whether that even should be a public function and whether you should encourage more use. And then we can look at the function declaration as well. Does it have a lot of parameters? Is there any complexity to its implementation? Does it have tests? Are there going to be lot of uses of the function? If the answer to all those questions is no, you could probably inline it without losing much. But the flip side is that you wouldn't gain much by doing so. A small function that is used a lot is probably somewhat valuable.
And there's a third thing that needs to be considered: does a function increase the API surface of your module. Having lots of private functions makes your module hard to understand. Having lots of public functions, makes the API less cohesive.
So, there's a grey area here. Languages like Kotlin give you a additional options: make it a nested function, make it an extension function, put it in a Companion object, etc. You can put functions in functions and those can help readability. The whole point of doing that is preventing usage outside the context of the outer function. Nested functions should probably be very short. And their only goal should be to make the outer function logic more readable/understandable. It's not something I use a lot but I've found a few uses for this. There's no point to using nested functions other than for readability.
And speaking of Kotlin, it's standard library is full of very small extension functions. Most of them are one or two lines. They are clearly valuable because people use them all the time. You get such gems as fun List.isNullOrEmpty(): Boolean which helps make your if statements a lot more readable and less flaky. Also works on Java lists. Stuff like that is a big part of why I like Kotlin.
I tend to dumb down a lot of advice like both are debating here to cohesiveness and coupling. In the context of functions, you get coupling via parameters and side effects (e.g. modifying state via parameters) instead of return values. And you lose cohesiveness if a single function starts doing too many not so related things. High coupling and low cohesiveness usually means poor testability. You'll find yourself mocking parameters just to be able to test a function. Improving testability is a valid reason for extracting smaller, easier to test functions.
What's the value of extracting a function that is used only once or twice. It's probably very limited. It's debatable whether that even should be a public function and whether you should encourage more use. And then we can look at the function declaration as well. Does it have a lot of parameters? Is there any complexity to its implementation? Does it have tests? Are there going to be lot of uses of the function? If the answer to all those questions is no, you could probably inline it without losing much. But the flip side is that you wouldn't gain much by doing so. A small function that is used a lot is probably somewhat valuable.
And there's a third thing that needs to be considered: does a function increase the API surface of your module. Having lots of private functions makes your module hard to understand. Having lots of public functions, makes the API less cohesive.
So, there's a grey area here. Languages like Kotlin give you a additional options: make it a nested function, make it an extension function, put it in a Companion object, etc. You can put functions in functions and those can help readability. The whole point of doing that is preventing usage outside the context of the outer function. Nested functions should probably be very short. And their only goal should be to make the outer function logic more readable/understandable. It's not something I use a lot but I've found a few uses for this. There's no point to using nested functions other than for readability.
And speaking of Kotlin, it's standard library is full of very small extension functions. Most of them are one or two lines. They are clearly valuable because people use them all the time. You get such gems as fun List.isNullOrEmpty(): Boolean which helps make your if statements a lot more readable and less flaky. Also works on Java lists. Stuff like that is a big part of why I like Kotlin.
I tend to dumb down a lot of advice like both are debating here to cohesiveness and coupling. In the context of functions, you get coupling via parameters and side effects (e.g. modifying state via parameters) instead of return values. And you lose cohesiveness if a single function starts doing too many not so related things. High coupling and low cohesiveness usually means poor testability. You'll find yourself mocking parameters just to be able to test a function. Improving testability is a valid reason for extracting smaller, easier to test functions.