Yep, At WOT in particular, the TB-to-oil filler-hose flows reverse of normal and vents blowby (to assist the PCV valve line).
PCV flow is most definately bi-directional.
WHATEVER YOU DO, DO NOT DELETE/PLUG YOUR PCV VALVE...trust me on this, my motor is in the machine shop RIGHT NOW because the person i bought the car from plugged the damn thing. just leave it alone.