Unlike Dropbox, Google Drive, and Microsoft, OneDrive doesn't seem to sync a folder on my PC. You have to manually drag files and folders to upload them. But free (I already have Prime) is a good price to backup my 500GB of photos.
Are you saying that the Amazon Cloud Drive client is allowing to access files on the cloud, that are not synchronized to your machine? If that is the case, this is a first, and it is great to hear!