>Didn’t Starlink redesign for that purpose once already

Brightness mitigation has generally been more of an ongoing process than a one-off, though they've just done a major revision that launched only yesterday. SpaceX are all about design iteration, and Starlink is no exception to that rule.

The details of their previous efforts can be found in this document, and the details for the new design can be found on page 3 of this document.