Thanks for that info, however I respectfully disagree about "not what it's for". I get everything else you say, and agree, however a more significant source of crankcase pressure than blow-by is boost leaking back through your PCV valve back into the crankcase, where it has nowhere else to go but out the valve cover breather line. Blow-by is nothing compared to that. Like I said, I don't know how well sealed the PCV valve is on these cars, but in the Subaru Legacy GT I had previously, I could expect no more than 20k miles on a PCV valve before it wasn't holding back 18 psi of boost.
My point then, was that by removing boost pressure from the PCV valve via a check valve, one substantially reduces the out flow of vapour from the valve cover breather line.
This is my hypothesis, and so I ask whether anyone else with dual cans and a check valve on the PCV side can, has any significant condensate accumulation on the breather side, because I had zero. Bone dry. I cleaned the lines before and after they were still clean and dry. Not even an oily residue. I'll do that again even. This tells me that while in theory it might seem to make sense to have two catch cans, in practice its not useful if you have the check valve.
But maybe others have different experience, yourself included?