Hello, @Ismael,
Alright, Thanks for whitelisting Pakistan I am able to check your issues now,
Now, I have checked and confirmed that the filter works like this. For example, there are two products with variants of “Size and Color”.
1st product has only the color variant.
2nd product has color and size variants
Now, when you search the filter by color it will show all the product that has the color variant in them because if a product has variants of size and color user must need to select both variants in order to add the product to the cart.
This is how it works and you cannot change it without customization.
Regarding the attribute, it is a WooCommerce function, and here is an article to know about the details of it: https://woocommerce.com/document/variable-product/
Regards 8Themes Team.