Why fluff is a fault - the Corgi is a working dog and need it's water resisting coat to perform the tasks it was ment for. Compare a wet fluff to a wet normal coat and I think you'll se the problem. Also the length of the coat and it's silkyness, anything sticks on it. Most likely the fluffy coat came when Corgis were crossbred with collies long time ago, so please let's stick to the standard. It was written at a time when they had a lot more experience with that particular problem.
Agility is the only place they are accepted.