Not completely true. Curry, Irving, and Paul all have excellent court vision and the ability to create for others, which are the essential qualities for a PG. The fact that they can light it up also makes them superstars. You can't take any talented SG and plug them into the PG position and be successful. Most players either have vision or they don't (sort of like good hands for a big). It's few and far between the players that can develop this quality all of a sudden at age 20.
You'd think we would have learned our lesson over the last decade with trying to convert SGs into PGs. Most of the time this doesn't work.
Having said that, I think DMW, though labeled as a combo guard, has much more potential to play PG than JCL. Coleman-Lands is about as pure of a SG is there is out there. After a year of watching him (plus all his H.S. videos), I've never once seen him get into the lane and create. OTOH, Da'Monte has that ability to get in the lane and make things happen.