Many biographies of JW detail his journey from the USMC to Navy medical to Howard University (Masters in English), and to Chicago Divinity School and United Theological Seminary. Unless those divinity schools have such a degree, I’d be inclined to doubt it.
He might have written such a paper for any of those schools, but that’s hardly the same thing as getting a master’s in the subject.
If you can get a Masters in English, you can probably get a Masters from a divinity school.
The Doctor of Ministry degree sounds like a Doctor of Education degree, meaning you don't actually have to know something. You have to write about how to teach it (or in this case, preach it).