Am I correct in assuming that since you're providing mixing codes, then it doesn't completely break the link between someone else's transactions and ours?
^{- While you're taking one thing out of the equation, you're leaving the rest in!}

It seems that there's no error in adding the same address with identical delays and distributions and based on the provided signed letter/message, I believe it counts each one of them as a separate address so it's going to unnecessarily add a slightly more fee!