Thats because most creatine comes from animals, so if Veggies suddenly introduce it to their bodies in larger amount than they are used to they will initially see bigger gains than people with normal diets until their metabolism adjusts because it isn't starved of creatine any more.

Its purely a result of lifestyle effects and nothing to do with a vegetarians body type, add the warning about cheap suppliments for veggies but the rest is not needed...