I actually believe there would be fewer UI bugs if more UI was modeled as a state machine. After all, all diagrams and design is often based on "when X is shown

I actually believe there would be fewer UI bugs if more UI was modeled as a state machine. After all, all diagrams and design is often based on "when X is shown and Y is pressed, we go to Z". But in code that's expressed in a way that makes it possible to have a mismatch between multiple half baked states.