Muscle confusion was this myth that your body got used to exercises and couldn't improve so you should change them frequently to "confuse" your muscles and prevent this. It's basically a misunderstand of what you're talking about where different exercises can bias different muscles or different portions of the same muscle mixed with not necessarily knowing what is currently limiting you on a lift.

Your post is well written and reasonable but (I think) for most people ultimately unanswerable. Not to be too pithy but this brings me back to the "the best routine is the one you'll do" stance.