Chen Hui Jing notes that when you absolutely position a flex item, it’s no longer part of the flex layout. Except… it kinda is a little bit. If you make the child position: absolute; but don’t apply any top/right/bottom/left properties, then flexbox alignment will still apply to it.
It’s odd to see, but it makes a certain sort of sense as well. When you apply position: absolute; to things (and nothing else), they kinda just stay where they are until you apply other positioning. Check out how this SVG icon just sits in the middle of this paragraph, and even flows with it on resize, because it doesn’t have any specific positioning instructions other than to not affect anything else.