Hilchot Berachot 6:18-20 (Can you avoid netilat yadayim by covering your hands while eating?)

The Rambam says that a person may wrap his hands in a napkin and thereby avoid netilat yadayim. He also says, however, that if a person uses a fork and does not touch the food, he needs netilat yadayim. What’s the difference between the two cases?