4G63T, as a former ASE master certified technician, I can tell you with absolute certainty that the positive crankcase ventilation system has a lot to do with oil leaks if it's not working properly. It's as simple as negative pressure versus positive pressure inside the engine. If the PCV valve system isn't working properly than eventually positive pressure, however so slight, will build up. Once positive pressure builds inside the engine, it will eventually push the oil past the seals.
Mike has a good point, there is no evidence that there is a problem with the Skyactiv engines. So I don't understand why anyone would mess with it. From what I have learned, carbon buildup on the intake valves was a problem when direct injection first came out. Only the early adopters of this technology had this problem. As far as I know, manufacturers have mostly solved this problem.
I'm on my second Skyactiv powertrain with a total of 80,000 miles cumulatively. Based on my experience, these engines are very well engineered and in my opinion bulletproof. The Skyactiv family of engines in my opinion are some of the best I have ever experienced. If Mazda made a Skyactiv V-8 engine and put it into a pick up truck then I would buy it in a heartbeat.