Many screen readers don't narrate whether sort has occured after invoking the column header. For example, nvaccess/nvda#10890.

Add a disclaimer that this is a known issue and also will occur for the APG reference implementations: https://www.w3.org/WAI/ARIA/apg/example-index/table/sortable-table