My guess here is that this won't do much because if the folder is empty, it won't really have any subfolders that you can go into. I think what you want is to delete empty folders, and the other folders, descend into. In such a case, you'd want to split this into two rules:
"If Kind is Folder, (stuff about date and size as you have it already), then Move to trash, do growl"
"If Kind is Folder, Run rules on folder contents"
Have the more specific rule appear first and any which don't match it will move on to the next one. That means the first rule will handle empty folders while the second rule will handle any non-empty folders (in which case, it will descend into it).
Try that out and let me know how it works.