He was paraphrasing Pascal: "I would have written a shorter letter, but I did not have the time".
I agree with the general point, but when a writer has a commercial relationship based on word counts, it changes the equation. I dislike word-count based contracts for that reason, but when the CEO of Widget Company Ltd hires me to ghost-write his blog articles, he isn't usually receptive to "you can have a 1000-word article for $400 or an 800-word article for $500".