Is there any point at which a particular spammy email will no longer show up in Junk?

The settings in your screenshot will make SpamSieve move the more spammy messages (score of 90/100) directly to Trash instead of Junk. This does not affect messages that were moved to Junk by a server junk filter (which you can identify by their lack of background color).

I think we set up the rescue script to move messages that the server junk filter moved to Junk to Trash. The script will run automatically if you attach it to a rule.