You'll also note that Mazda, in their very own technical bulletin, states that they believe the issues to be precisely what I said they were.
To quote, "This condition may be the result of the turbo's oil supply not being able to adequately drain out of the turbo during long idle periods. Explain to the customer that MAZDA is currently working on an improved positive crankcase valve (PCV) system to reduce the engine crankcase pressures to allow the turbo's oil supply to drain from the turbocharger more efficiently."
If Mazda doesn't know their own vehicles, just who would?
BTW, "Turbo 101" is that the oil return line flow should be unrestricted. Otherwise, the resulting pressurization of the core causes oil to seep past the seals. When the crankcase is itself pressurizing, you get the same result. This isn't rocket science, people who don't understand it just make it seem that way.