Obviously, you don’t believe that a copyleft license should trump other licenses (or lack thereof)

I’m not sure what you mean. No licenses “trump” any other license; that’s not how it works. You can only make something that’s a derivative work of multiple differently-licensed things if the terms of all the licenses allow it, something the FSF calls “compatibility.” Obviously, a proprietary license can never be compatible with a copyleft one, so what I’m hoping to achieve is a ruling that says any AI whose training dataset included both copyleft and proprietary items has completely legally-unusable output. (And also that any AI whose training dataset includes copyleft items along with permissively-licensed and public domain ones must have its output be copyleft.)