cfor,
If I look at the disk there are delta files when VAAI is turned on, also the datastore and fast provisioning is turned on, so it is not doing what the settings say should be happening. Also looking at the vmdk files they show isNativeSnapshot="no" and createType="vmfsSparse" when VAAI is turned on and fastprovisioning is turned on. Once I turn off fast provisioning the clones are still just as fast but are done by VAAI because when I look at the descriptor file it looks no different from the source it was cloning from.
This is happening across two different array manufactures that both support VAAI (Tintri and NetApp)