^This is the statement I'm getting at with my previous post.
I'm guessing by "oil getting past the cylinders" you meant oil getting past the piston rings. Because that's exactly how unvaporized, and therefore unburned fuel gets into the oil. As you already mentioned - it's a common problem on GDI engines and is amplified by forced induction. Since increased cylinder pressures from tubocharger/supercharger "help" push the unburned fuel past the piston rings and into the oil. That's why engines with longer warm-up times and/or short trips see higher fuel dilution than the same engine running on the highway most of the time.
Does that make it a little easier to see how the oil type affects fuel dilution? Higher HTHS oil seems to create a better seal between the rings and cylinder walls. Some fuel still gets through, but not as much.