it makes sense on Tohno, because it's big enough. I feel that the small chans would be better off having a 2D board, maybe a /jp/ and then something like /lounge/ but without the shitposting. Enforcing strict anime-only rules whilst your site is small is just going to discourage people from posting there. Obviously discouraging /b/tards and the like is a good thing, but I know that I have other interests other than anime.
That said Sama does allow some off topic threads in /z/ sometimes. Sometimes being the key word here.