React docs on useEffect

The docs have an example about using useEffect with cleanup, here.

If I carry out the sequence, then I would get
run effect -> subscribe to update from ChatApi -> setIsOnline -> cleanup -> run effect -> subscribe to update from ChatApi -> setIsOnline

I am unsure as to why this does not lead to an infinite loop without use of the dependency array?

One understanding / theory that I have is:
The first time the subscription cause setIsOnline(true). Next time (after one cycle of unsubscribe/effect), the setIsOnline gets argument as true and hence further update to the component does not occur. This is assuming that this form of setIsOnline does not re-render if the isOnline has not changed (it is still true).

I am curious as to why the piece of code is correct.

Here it is as copied from the useEffect documentation

import React, { useState, useEffect } from 'react';

function FriendStatus(props) {
  const [isOnline, setIsOnline] = useState(null);

  useEffect(() => {
    function handleStatusChange(status) {
      setIsOnline(status.isOnline);
    }
    ChatAPI.subscribeToFriendStatus(props.friend.id, handleStatusChange);
    // Specify how to clean up after this effect:
    return function cleanup() {
      ChatAPI.unsubscribeFromFriendStatus(props.friend.id, handleStatusChange);
    };
  });

  if (isOnline === null) {
    return 'Loading...';
  }
  return isOnline ? 'Online' : 'Offline';
}

リンク先の useEffect ドキュメントの例から始め、説明されている subscription、cleanup、setIsOnline の順序を確認してください。例に再レンダーの動作の説明が必要なのか、改訂した例が必要なのかを明確にし、その後、期待される effect のライフサイクルと完了基準が明示されるようにドキュメントを更新してください。