/vmfs/volumes/fce81637-c1fff466 # du -h lv-win2016test/*.vmdk
16.0K lv-win2016test/lv-win2016test-flat.vmdk
4.0K lv-win2016test/lv-win2016test.vmdk
17.6G lv-win2016test/lv-win2016test_1-flat.vmdk
4.0K lv-win2016test/lv-win2016test_1.vmdk
That's the space that's consumed on the datastore.
Thin provisioning on a VMFS datastore is file system feature, i.e. not like sparse files as they are used in e.g. VMware Player, or Workstation. Tool which do not support this feature will "see" a full provisioned file. Any previously unused data block is internally referred to by a NULL pointer, and an application, or tool - which isn't aware of this - reading such a data block will receive zeroes as the response.
On native Linux file systems the tar command has an option to handle sparse files, but that's unfortunately not available for VMFS file systems (at least I'm not aware of it). In order to transfer virtual disks from one host to another with maintaining thin provisioning you'll need to use tools which support thin provisioning. This can be achieved by e.g. using export/import as OFV, using the ovftool to copy virtual machines directly from one host to another (see e.g. https://www.virtuallyghetto.com/2012/06/how-to-copy-vms-directly-between-esxi.html), or by using a backup application which supports this
I don't understand lv-win2016test_1-flat.vmdk which has "_1" and "-flat", how was it created?
By default, virtual disks are named <vmname>.vmdk for the first one, <vmname>_1.vmdk for the second one, ...
In this case it looks like someone created a virtual machine, then removed the first virtual disk from the configuration without deleting it from the disk, and then created another virtual disk. I'm pretty sure that lv-win2016test.vmdk isn't used, because its flat.vmdk file still has the initial size of 16kB. To find out about this, check the VM's configuration (.vmx) file, and/or the VM's latest vmware.log file to see whether this file is referenced. Alernatively you may run RVTools (https://www.robware.net/rvtools/) which reports unused files as Zombies in its vHealth tab.
André