All documents shown rather than none?

This is an observation in case it is significant.

I was expecting to see no documents on the test server's web pages once the DL Listing objects had lost their categories upon the upgrade. However, what we get is the opposite - batched output showing what appears to be every document in the library (some 39 'pages' of document links).

I assume this is due to the different techniques used to read the categories in the DL Listing object (where previously there had to be an available document in the category to be abe to see it in the DL Listing categories list, but now you see all of them regardless).