I've read On Writing, though not recently. The strong impression I have is that his advice was intended as just that -- advice, rather than binding pronouncements.

That is, King in On Writing seems essentially to be saying "Here's what worked for me. Maybe it will work for you, too," rather than trying to be Moses on the flank of Mount Sinai.

And, for any wordsmith, much of his advice has value! Certainly there's no doubt of that. On the other hand, King is a writer of horror fiction, and I am not. This, at the very least, suggests that not all of his advice will be applicable to my purpose, a consideration which seemed absent from the comment originating this thread.