bi-directional cross-filtering

Why is this an example of bi-directional filtering? At first, for the single-directional case, you filtered the fact table based on the dim_product table. Then, for the so-called "bi-directional" case, you filtered columns part of the original dim_product table based on the color column of the same dim table!? by bi-directional I would have expected to filter the dim table based on the fact table..