It's more of a client side filter. Notes are still retrieved, they're just not displayed.
Discussion
That's what I figured. We need a relay that we can self host and connect to when on mobile that filters out all unwanted content from being retrieved. We will have to wait and see if relay to relay communication happens. That way when I am on mobile I am only connected to my self hosted relay. The self hosted relay would do all the filtering for the mobile client.