I think they just love to refer the red flags with red hair to make it easier for the viewers/readers to differentiate lol 😂 jk-. I also think they have a grudge against the redheads
-completed mangas:780+
-list of all my completed BLs: https://mangabuddy.com/manga-list/82080
-short Yaoi manga list:
https://mangabuddy.com/manga-list/141110
-stan seventeen for a happy life! 😉