Chrome：当伪元素超出屏幕时，z-index不适用于伪元素

Question

请参阅：https://codepen.io/hyperzlib/pen/GRoVova

.bgcover {
  position: fixed;
  background-color: white;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: -2;
}

.box {
  position: relative;
  width: 100px;
  height: 200px;
  margin: 1em;
  padding-left: 4em;
}

.box::after {
  position: absolute;
  content: 'test';
  z-index: -1;
  transition: opacity 250ms linear;
  opacity: 0;
  width: 100%;
  height: 100%;
  left: 0;
  top: 0;
}

.box::after {
  opacity: 1;
}

<div class="bgcover"></div>
<div class="box">box 1</div>
<div class="box">box 2</div>
<div class="box">box 3</div>
<div class="box">box 4</div>
<div class="box">box 5</div>
<div class="box">box 6</div>
<div class="box">box 7</div>
<div class="box">box 8</div>
<div class="box">box 9</div>
<div class="box">box 10</div>

Chrome上的结果：Result on chrome

Firefox上的结果：Result on firefox

如果在页面加载时屏幕外出现伪元素（z索引：-1），它将被背景div（z索引：-2）覆盖。

此错误仅在Chrome上引起。