I believe it is more that then anything else.
Earlier engines just had breathers.
To my mind if you pull a vacume to the PVC valve the gasses go into the intake.
The air to keep the crank case from pulling a strong vacume and sucking oil etc down from around the rings comes from the other breather.
The air that goes into that breather IMHO should be filtered so fine dust does not enter the crankcase under vacume that would open the PVC