Basically it was a thoughtless joke that wasn't intended to be offensive, but due to the team being quite homogeneous, it didn't occur to anyone why Bow, as a black character, having a brother called "Sow" who "works the fields" might come across as offensive given the historical context.
https://comicyears.com/pop-culture/she-ra-creators-face-social-media-backlash-over-a-joke-during-livestream-panel/
They apologised for it, but it did lead to a wider discussion about lack of racial diversity in the industry and on that stream.
