The Urban legend would make sense... for an air cooled engine. If it's not getting ample air flow, it'll overheat. But my guess is that if the VW is moving, it had plenty of air...
I am opposed to drafting a big rig. That said, I do sometimes get behind one and see where the draft ends. I use the scangauge instant mileage. On a very calm day one can get the effects of "some draft" by staying way back. I do that on occassion. On a windy day, forget it. The instant mileage readout on the scangauge or ultra gauge is worth the price of the units to me. I constantly scan the instant. Sometimes one can click the cruise off one click and see 5 mpg difference. I realize many don't care for the instant readout but I have been using one for several years. Just how I have trained myself to increase my mileage. Dan