What is the purpose of ‘key’ prop in Venia Shimmer component?

In some Venia components (for example in @magento/venia-ui/lib/RootComponents/Product/product.shimmer.js) <Shimmer> has “key” prop:

...
<Shimmer width="100%" height={2} key="product-name" />
    <div className={classes.productPrice}>
        <Shimmer width={3} height={2} key="product-price" />
    </div>
...

What is it’s purpose, considering that <Shimmer> is rendered as a <div> and not a list? I couldn’t find anything in documentation about it.