You obviously don’t understand how WordPress, or “the business of making code,” works. I gave you a solution to your issue, and it’s up to you whether or not you’re willing to put forth the effort in testing your own website.

Your “major vendor” theme author is no different to me than any of the other hundreds of thousands of WordPress themes that exist. I can’t possibly know, or pretend to know, what is and is not compatible with every WordPress theme. There could be no compatibility issues with the theme itself, however maybe your web server isn’t running a current version of PHP. There are infinite issues that can arise when related to compatibility and it’s not up to WordPress plugin developers (who are creating plugins for the community for free) to test compatibility with every theme.

As you can see by the plugin information, it’s tested compatible with WordPress version 4.9.1, so the real question is if your theme is compatible.

To your final point:

I think there IS a way that you can find out, and are choosing not too. What tech question can I ask of the nice people over at Divi to see if it will work? I am sure there is a way to find out without cutting up my website in the process?

If you tell me how this could possibly be done, knock yourself out.