Not necessary, but the source used for the images displayed (there are others on the website explaining what it does) has a bias in that direction which is stronger then the bias you find in e.g. Animes on crunchyroll or similar.
EDIT: It also a very reasonable source as it's very hard to get large amount of anime/manga images which mostly are in color, which more importantly are tagged and you know you will most likely not get in trouble for using them.
