Must the render function VNodes be unique in vuejs?

vuejs official website tutorial:
ide/render-function.html-sharp%E7%BA%A6%E6%9D%9F" rel=" nofollow noreferrer "> VNodes must be unique

All VNodes in the

component tree must be unique. This means that the following render function is invalid: 

render: function (createElement) {
  var myParagraphVNode = createElement("p", "hi")
  return createElement("div", [
    // - VNodes
    myParagraphVNode, myParagraphVNode
  ])
}

but the result of my test is that the above code is OK. The test address is as follows:
https://codepen.io/quiettroja.
running result is normal:

clipboard.png

Why is it inconsistent with the conclusion of the official website?

Vue.js
Aug.02,2021

rendering is fine, and there will be problems with subsequent operations. The above code scenario is too simple, so try to replace it with complex scenarios.
someone has already explained the VNode constraint problem of vue. see for details.

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