it seems that I got the same misunderstanding of the "background"-thingy in the first place. Seems that there is a confusion between 'background transfer' and 'queues'...
Could be helpful to read the help of this feature again:
I think what Novasource expected to happen was that if you select a folder with several files in it, all the files are transferred simultanously. But WinSCP doesn't 'resolve' the contents of the folder but it transfers one file after the other.
But if you drag 5 folders one after the other to the WinSCP window, the program creates 5 different queues.
That's something SmartFTP handles a different way by creating several queues automatically.