Filezilla on windows assumes sftp to be SSH transfers. So I think you've got that backwards.
What, exactly, do you think I have backwards? I just tried to explain how wildly diverse the meanings are, and how people use the terms. I don't care what your favorite FTP client means when it uses the term SFTP (bully for you, that you happen to use one that uses the term correctly)...I'm telling you that there is little agreement in the wild about what the term means, and many people use it incorrectly to refer to FTPS (and other kinds of secured FTP).