I’m finding the posts challenging to understand. I suspect you may be using the term CPU incorrectly.

As was pointed out above, if you’re flying on a short-haul international flight, you would almost always be CPU eligible. To be eligible, you would have to have status. To secure upgrades regularly, you’d certainly have status higher than Silver. If you’re Gold or higher on an international flight, you would have access to the United Club based on status alone. You would be able to access the Club regardless of whether you’re in coach or first class.