Thin provisioning is a file system feature, i.e. not comparable to e.g. sparse files in VMware Workstation.
So when you look at the files using a tool that's not aware of this feature (or which doesn't expose it), you will only see the provisioned size.
If you want to see the real size of a flat file from e.g. the command line, you may run e.g. ls -lisa which will show the used blocks (in kB) in the second column.
André