I’m of the opinion many designers*, including some very good designers, don’t specifically know. They have intuition, and some loose non-scientific testing, and are guessing and hoping. 

If they try and actually put it down in cold hard words then they can be held responsible for it. And they have to be right about it — because if their intuition tells them one thing and they say it out loud and folks start driving at that rather than doing what the system actually evokes… it can take the wheels out. 

So, folks play coy. They pretend they know exactly, when they actually don’t and are guessing as much (or almost as much) as everyone else. 

*Not all designers, obviously. This is not about ethics in game emergence conversation. 

That said, for designers who can do it, I fucking fully support doing it. Like, 100% alignment with the OP.