[super vw]

I also think most of them are "stamped" or "punched" to give it a better look and make it stronger. So the hole would have a little lip/dip in it.
I am not to sure if people do just a square hole (kinda a oximorron eh?) or not, but i dont see why it would matter as the rear apron is not a main structural part. so punched or not, whatever works for you. i think the dies used to do the punch are kinda spendy though.

Later
Jonathan