Maybe you use ansible in a more complex environment than I do. I use ansible to provision servers, and jinja2 filters are some of the least-used things for me. I try to keep my ansible roles short and simple, and needing obscure jinja2 filters is a clue to me that I might be getting too fancy.

That said, when I have a question about jinja2, I find that the jinja2 docs are better than the ansible docs.