The video says if you can't talk you can write to Siri. That's misleading. It only lets you "edit" text you have already spoken. There is a feature in accessibility where you can enable siri text submissions without having to use your voice, but then that completely disables voice siri, meaning you can't do both.
Hopefully this gets fixed as most of the time use Voice Siri but would love like how I use pull down for spotlight a million times a day would be great to be able to enter siri questions into spotlight. Toggling an accessibility feature on an off each time defeats the purpose of trying to save time by using siri in the first place.