WinSCP can support keepuptodate from local to remote because Windows has functionality to notify an application when particular file changes. There's no way how to receive such notification from remote server via SSH/SCP/SFTP. The only way would be to periodically check all files. You can do that already by scheduling regular synchronization.

I saw winscp only support keepuptodate from local to remote,but not keepuptodate from remote to local,that's exactly I want,so can you develop this feature?