Because it seemed as though the ones you sent in the admin channel yesterday were the only ones you found that were incorrect, and there have been quite a few students that I've brought up after your checking that you missed and also had to fix. Better to have more people checking to catch everyone than just one and people maybe get missed.
If you check the notes I made, there's a lot of comments on things besides just being on the roster or not, which you weren't checking for and would have gotten missed (waitlisting, levels not being right for the dancer, etc) things that I have insight on that you may not. That's why we both work together