I believe Honda intent is to push air into the valve cover in order to force the oily air out the factory pcv box/valve due to the side in which the factory slash cut is done. The system relies upon the engine vacuum at idle pulling on the pcv valve and then at higher rpms full throttle (no vacuum) to use the velocity of the incoming air on the slash cut tube in the intake pipe to force the breathing. So basically at idle using manifold vacuum and at wide open when there is little manifold vauum using intake velocity.
Honda wasn't really designing around 12:1 compression na motors going to 9k+ or cars running 30 lbs of boost. In those cases the crankcase builds up too much pressure that this system no longer works and that is why on those apps a crankcase breather system either veting to atmosphere or being mechanically ventilated by other means.
iv never felt air comming out of the intake tube while the throttle was open...of course i never felt it at WOT with load on the engine but as far i as can tell air is always comming out of the valve cover and being sucked into the intake tube. and therefore a filter is pointless. just connect it up like honda did unless you have some sorta forced induction.