In response to the comment about crankcase pressure. I do agree that it was a pollution device to burn the crankcase vapors. However, those crankcase "vapors" add up to a pressure as they accumulate.The breathers allow it to escape, but the draw of the PCV helps remove it. Modern engines wind much higher than the ones that were around when the PCV was first created, it may be that they weren't generating enough pressures to have a problem. I have seen an engine that leaked from various areas until a PCV was plumbed in, so I stand by my position. Sometimes there are side benefits that are not part of the initial application.
One of the reasons that it is applied to only one valve cover is so there can be fresh air drawn in from the other side. I would have to look at the plumbing on the Corvette you mention, but it has to have fresh air tube connected somewhere...possibly on the
oil fill tube leading to the intake tract somewhere.