I think you might be taking what was intended to be a simple example a little too far. That said, "pushbutton" could very well be limited to the values 0 and 1

I think you might be taking what was intended to be a simple example a little too far. That said, "pushbutton" could very well be limited to the values 0 and 1 during the keypad scanning, debouncing and decoding code. Chill bro.