Porsche has always used every possible loophole in the rules they could, all the way to stealing a world championship that did not belong to them in 1982. The Group-C Rondeau-Ford was effectively beating Porsche that year in points, the first year of the 956, because of the early results gained by the French tiny manufacturer, with a notable a win at Monza and good other placings.
So the crafty krauts fished some points gained by a privately entered GT entry at the Nurburgring to fatten their total. The thing is, this nearly stock 930 had a few infractions to the GT rules regarding what was allowed or not, so it got classified as a "Prototype", or...Group-C. Hence the "available" points for the 956's.
The FIA did not want to tell Porsche to go fish because their pond was not so big, so the little Rondeau team was robbed of a well-deserved title, by a single point.
Love their cars, hate these guys.