I really don't know what basis you have to say that, but let me disagree. First, now hulu don't have .flv extensions anymore since there are so many software on the market which are able to download movies, it has only rtmpe. The 3 software you recommended they don't download rtmpe files, rtmpe can only be recorded by screen capturing. Those 3 software can support flv, not rtmpe.
Tunebite capture all the images u select for capturing.