Ohhhh, sweet, the secret is index.php. Found the problem. Thanks, man. You are a hero to me and my people.
To any future wonderers, Divi is bonkers and is a creature of its own. It extends into the realms of insanity far beyond normal wordpress. If you’re using the blog module on a page that’s not the designated page for posts, it will use page.php to create the page and I dunno, magically make your blog. I had to set this page to be the posts page in Settings -> Reading, and now it will make it with index.php, which you can edit. So that’s nice.
