The sftp-config.json is ignored unless the user explicitly opens the file, or right-clicks on it and uploads it.
This is an untruth.
Try it out for yourselves:
- Use ST2 or ST3
- edit your sftp-config.json file by simply changing anything inside it
- save it as you would any other local file in STx
- connect to and browse your server
- look in the document root and see what you find
No other FTP programs on the client machine are in use.