What should happen to the position-anchored element when the anchor is in top layer?

A quick test on today's implementation shows that the positioning fails silently when the anchor is in top layer but the positioned element is not already in top layer.

As an example, consider a modal <dialog> or a popover element that's open in the top layer. Now, consider a non top-layer element that's outside this dialog/popover. If I want to anchor this element to something within the dialog/popover, it will not appear in the top layer.

Would it make sense to automatically elevate positioned elements (and pseudo-elements) into the top layer when their anchors are also in the top layer?