thats the thing grasscarp, the recipe says 'grate potatoes, place in a sieve and squeeze out any excess water', which is fine but when I am doing anything with potatoes I always rinse them to remove excess starch (force of habit perhaps), maybe its not so important in this method.
If you mean rinse the potatoes after you have grated them, then no. Don't do it.
I would par boil the pots (10 minutes). Let them cool. Then grate them. Then sprinkle them with salt and squeeze them in a clean cloth to get rid of the excess moisture. That help to stop them going soggy when you fry them.