I haven't seen this topic listed in the feature requests.
I have to disagree with you about it being a 'feature', since the objective of an FTP task is to transfer files, if no file transfer takes place, it obviously failed. I can't think of any condition under which the failure to transfer a file using an FTP task could be considered a 'success'.
When I go to my supervisor to explain why a vendor didn't receive their file, which has monetary implications, that they had to have received the file because the task shows it to have executed successfully. It doesn't not give your product, or myself, any validity.
I am currently revamping all my ftp tasks, which are numerous, to check a condition after the task executes, whether successfully or not, to see if the given file was transferred and throw an error message if it didn't. It would save myself and I'm sure alot of people extra work to test if a given ftp task actually transferred a file before it could be considered 'successful' or not.
It would make things much easier if the absence of a file transfer on an FTP task triggered a failure of the task and therefore the job. This way, we can stop everything and manually intervene.