Your description is a little unclear to me, Phil (sorry).
Is the PCV tube the "stand pipe" that you refer-to? Most likely?
Your description sounds right since the PCV fitting is higher above the "draft hole" in the block on the GM PCV "draft tubes" (compared to the "height" in a standard road-draft tube.
This was an attempt to avoid "oil-mist" from fouling the PCV, when that "mist" was drafted/filtered out from between the PCV and the lower block and the oil pan.
