This has been fixed in version 7.0U2 and later
Workaround:
If upgrading to 7.0U2 is not possible at this time, to ensure that the vCenter UI correctly reflects the license status for the vSAN Appliance, perform the below steps:
1. Disconnect the Witness from the vCenter [Right Click on the Host -> Connection -> Disconnect -> OK
2. Connect the Witness back to the vCenter [Right Click on the disconnected Host -> Connection -> Connect --> OK
3. Verify that the Witness is correctly licensed with an Embedded OEM License.
Note: Ensure the witness appliance is not in maintenance mode when performing the above workaround, otherwise the license information won't update.