skane,
Years ago I heard an old timer say that donuts had holes because of the poor quality control of heating/cooking back in the day. The center was often under cooked and customers complained. Bakers tried many ways of getting around this problem, but found the simple solution of cutting out the center and frying that separately. Don't know if it's true or not, but does make sense.
grizzly bare
not a LEO any more but I still love my donuts