Well a lot also depends on what these tests were, if they were basically on-demand scans that would make quite a difference. As if they just used the pre-defined scans, Quick or Full they don't even look for PUPs and keyloggers fall into this category also.
On-demand scans for the most part are going to be scanning inert or dormant files, whereas the resident shield (FSS) scans for Viruses, PUPs and Suspicious files that are executed.
So if these files were dormant they wouldn't be detected but if run that would be a different ball game.