[EdKiefer]

The problem people are having is the stock OEM PCV system is "closed loop" system, meaning any blow-by gases are not allowed to get to atmosphere .
Since OEM and dyno-valve both are connected to stock intake PCV hose, the max vacuum that can draw blow-by is the same .

This vacuum issue, I can only imagine is slightly lower vacuum at idle conditions as this is were blow-by is generally low, vacuum is high and throttle is low % .

So here I can see if might be able to maintain slightly higher vacuum conditions . how much that affects anything, I don't know. also in affect if adjusted(closed position) to much you might not get enough draw at idle .

does dyno-valve use pressure sensor on crankcase vacuum so it maintains decent amount . you never want to see pressure as this can lead to leaks .

Edit: I forgot to mention modern EFI that has DBW and MAF sensor will keep monitor on any airflow that bypasses throttle body as compared to old carb, throttlebody or even speed density FI systems .
So I have hard time seeing were this would help on modern systems .