I just noticed that Alfred's search results for Safari's reading list shows already read items. I'd understand if this is a detail which some user might find useful but I think it would be helpful if there would at least be a toggle in Alfred to include/exclude read items from the reading list. Strictly speaking, excluding read items should in my opinion be the default, as the reading list was conceived that way - if you open an item from the reading list in Safari, the item is marked as read and not deleted.
To "replicate" the behavior, open the Alfred search bar and type in a title from one of Safari's "reading list" items, which is hidden in the reading list while the "unread" toggle is turned on.
Please let me know if I need to provide more details. Thanks for looking in to this.
I'm using Alfred version 4.0.3.  and macOS version 10.14.5 (18F132).