Hey Jamal,
I've finished making preparations replicating the issue in your controlled environment.
The only thing I carried over in bulk was the child theme that I use to make customizations to Divi, and then I removed all but the most important features. The functions.php only has scripts that ensure that the styles take precedence over theme and plugins, one that pulls the Divi logo from the field in the Divi options, and one that loads in widget areas.
I rebuilt everything else by hand, as I have it on my lien caché template staging environment. Including building the header and footer areas in the Divi Theme Builder whilst the rest of the layouts are structured in Toolset Layouts, particularly WooCommerce's Product layout.
I still encounter the issue.
Attached are a couple images that illustrate this issue. Exhibit A features my Divi child theme, which loads in my styles to make things look somewhat functional. The left panel shows what the header looks like on WooCommerce page layouts, and the right panel shows what it should like on a standard WP page.
In Exhibit B, however, I only have Divi proper activated, which does not load any custom functionality or styles from my child theme. And while all the styles break, you can still see that the custom global header and footer areas appear to properly load their elements, as made evidenced by the footer bar text that says "This is a Custom Footer Bar".
Just so you know, Jamal, we are actually actively attempting to abandon the Divi Integration Plugin, as neither lien caché or lien caché have this plugin installed. The goal was to use Divi's own Theme Builder to structure the global header and footer areas, and then have the child layouts built out with Toolset Layouts. We found that using the Theme Builder for everything proved problematic for some Toolset shortcodes, such as the conditional logic containers, and there are certain limitations that the Theme Builder has that Toolset Layouts takes care of for us, such as complex, filterable, archive loop outputs, which are simply not possible with the Theme Builder.
Solving this problem will allow us to move away from the Divi Integration Plugin, and therefore help us move into integration with Toolset Blocks when it has all the same features of Views and Layouts that we've come to rely on for the past four or so years we've been using your platform.