That doesn’t mean what you think it means, to paraphrase a popular movie quote. :-)
What do you think he thinks it means? It seems pretty clear — if you write in the name of a person who is already on the ballot, it counts just as if the person had registered as a write-in.
Unless — they decide that the REASON you wrote in the name was to “mark” your ballot so that someone would know YOU were the one who voted the ballot. And they have to find OTHER evidence of ballot-marking in order to determine that.