It's not hard to intuit, but yes it can be less useful owing to ambiguity and confusion. It would be less difficult to settle on a definition that does not lean so hard on "processing" and actually conveys what is problematic.

For example, "shelf-stable packaged foods with a large flour component, wherein the flour component is stripped of all fiber, with added fat, salt, and sometimes sugar". You can also include candy, soft-drinks and juice.

That doesn't tell you something is "ultra-processed", but it identifies more meaningful factors. These are typically non-satiating snack foods, very low in protein and fiber, but very savory with added salt and fat. The combination of refined flour, salt and fat seems to be of particular note (and sugar regardless).