Oh No! Your toilet clogged, is now overflowing, and can't be stopped! How did this ever happen? If only there had been some reminder on display that tells you how to properly handle this toilet to prevent an unfortunate event like this from happening...
Oh hey flyer with instructions from Dad! Dad has wrestled with the toilet monsters before in his youth. Dad knows it is not a demon to mess with. That is why Dad puts up specific instructions on how to handle the beast. These phrases of wisdom range from "If it's brown, flush it down" to "we aim to keep this bathroom clean, so your aim is appreciated."
Dad isn't telling you to "hold down lever all the way" simply for his sake. But Dad also wants to save you the embarrassment of having your residue left over for others to discover. And it is just common courtesy. Everyone assumes what you did based on your time spent in there, but no one needs confirmation. And if there is a problem, you're not cleaning it up, Dad is. And Dad can't afford time away from His Chair to deal with your mistakes.
Just follow the instructions.