You are correct to be hesitant to blank it off. A certain amount of blowby is normal, even in a new engine, and that blowby has a a lot of water vapor in it. The PVC keeps the water vapor swept out of your crankcase so it does not mix with your oil and cause foam and sludge.
The gas coming from the crankcase always has oil droplets suspended in it. The PVC has a cyclone separator in it so the oil droplets drain down to the oil pan and the rest of the blowby goes into the intake manifold behind the throttle.
Ideally, the PVC pulls a slight vacuum in the crankcase, pulling fresh filtered air from the air tube upstream of the throttle valve through a vent hose to the crankcase. This fresh air replaces the damp air and blowby that the PVC is drawing out. The oil droplets are separated in the PVC, and the remaining blowby air and water vapor goes to the intake manifold downstream of the throttle valve. If the PVC is not working, or there is excessive blowby, the crankcase pressurizes and the blowby comes out of the vent that is supposed to carry fresh filtered air in. The oil droplets in that blowby gunk up the intake tube and throttle body and idle air control and cause all kinds of grief.
If the car has several hundred thousand km on it, there will be so much blowby at high RPM that it will come backwards up the vent tube and gunk up the throttle body and idle air control valve a bit. This is normal for older cars (I know all about older cars, I have several). That is why you can drive a car the first 10 years without ever cleaning the throttle body, but by the time the car is 20 years old, you have to clean the throttle body at least once a year.