There’s like. Two references to him liking anime in Homestuck proper, and it’s sort of part of his aesthetic. And Tumblr is a lot more interested in Anime than it is in Philosophy, so when it came time to use Dirk in fandom culture, he kind of got boiled down to the interest or sets of interests that fans found most relatable or humorous, instead of the core traits that actually inform and flesh out his character. 

So basically: A little bit of canon and a whole lot of fanon, like a lot of things in Homestuck.