That's correct (because +100%, 0% and -100% can be seen as prudent money management), and especially very true for the professionals who manage long-only funds.
But How to do it well is a question!
just Unsure whether it's the "only true edge" or not. my guess is Probably Not!
Prudent money management is most certainly the only true edge in trading. In the fullness of time. I believe you will come to realize this as well.
Sadly, this is incorrect. It truly is the implementation of prudent money management that is the only true edge in successful trading. Anyone can forecast direction using a myriad of techniques. Those are not edges. --Practicing prudent money management is an edge though.