Have you done a second legend clear within the 20 minutes to see if that drops the catalyst - make sure you are claiming the chest. Your PGCR for the last run was 34 mins which may be the reason why the catalyst didn't drop since the time limit is supposed to be 20. Bungie mentioned in another thread that looks like its a text bug and its meant to say you need to obtain the catalyst. https://www.bungie.net/en/Forums/Post/263936997