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';
}

从链接的 useEffect 文档示例开始，检查其中描述的 subscription、cleanup 和 setIsOnline 顺序。明确该示例是否需要解释其重新渲染行为，或是否需要修改后的示例，然后更新文档，使预期的 effect 生命周期和完成标准清晰明确。