Why does cleanUp runs on only unmount if dependencies array is empty in React?

The react documentation says, If you want to run an effect and clean it up only once (on mount and unmount), you can pass an empty array ([]) as a second argument.

But it is in controdiction with the behaviour if some values are passed to dependency array in useEffect.

e.g:

useEffect(()=> {
  console.log('effect ran')
  return cleanupAction(){console.log('cleanup action')}
}, [props.value])

Here for every render when the effect will run, a cleanup will run before next render. so, cleanup will only run if the effect was run.

but in other scenario.

useEffect(()=> {
  console.log('effect ran')
  return cleanupAction(){console.log('cleanup action')}
}, [])

Here in this case, the effect will run only on first render. and I expect the cleanup to run only before the second render. Then, why does the cleanup runs on unmount.

Because, I assume, when a render caused a effect to run. a cleanup will run before next render. So, it is not happening in this case.