What I'm saying is that they can see organic debris. They can see that the machine is dirty. Whether or not it's actually contaminated with listeria or any other microbial at that time wouldn't be known until after a test.
So the test would still take place. Don't get me wrong. I'm certainly not trying to undercut the value of doing the testing. It's very important. But the visual observations that an inspector makes, which are then supported by the tests, are even better, because that trains the inspectors to do the prevention part of their work.
Inspectors in the past have seen debris on the machines and ordered them taken apart. The manufacturer's specifications weren't good enough.