For a sidebar alone, you don't need CSS grid (probably obvious). The point of this article, i.e. having something full-bleed, is implemented by adding a specific class to the element. Which means you would always have a DOM similar to

    </something that gets closed>
    <full bleed>
    ...
    </full bleed>
    <next>
    ...

My point is that now, with a new block element in the hierarchy, it would fill the maximum width anyway. It is only because of being inside a CSS grid that you now have to work around the grid positioning which means adding more CSS attributes.

The exception would be if you would want the full bleed element directly under the sidebar (in terms of z-index). Here CSS grid is useful, but this is probably a special case anyway.