If I understand correctly, the alerts can be classified under the different categories listed in the options (amber, extreme threats, etc…) and those can be disabled. However there is a categry called “presidential alerts” and those cannot be disabled.
Lucky for me, my province just blankets everything under “presidential alerts” and so that’s why the sliders don’t do anything in my case. Like… they should, but because my province just sends everything as super mega extreme presidential alerts, the options are useless.