CSS's display: none already affects what the screenreaders can "see." So it's already involved.

And getting sick is a great reason you might use the phone to call into work but it doesn't imply getting sick is therefor the way to run all other phone usage through. I.e. it changes the behavior of the screen reader because it hides the content of the document and a screen reader knows it doesn't make sense to read content that was removed but that doesn't provide any support for why content which only affects screen readers belongs in the styling language as well.

Further point, in case you still disagree whether it makes sense for CSS to include the ability or not: CSS supports pseudo-elements but that doesn't mean tags in your page should be turned into pseudo-elements just because you can.

> I wonder if a whitespace <div> with a right aria-label could fit the bill.

Aria-label only works on interactive elements. I believe except the div has a `role`, screenreaders will ignore the label.