During the creation of the Customization Specification template you are able to add the VM to Active Directory. The disadvantage is that the computer objects will be created in the Computers folder in Active Directory.  After the creation you will have to move the computer objects to desired OU.

There are 2 ways to workaround this issue:

1. pre-create the computer object in the destination OU when using Full VM's and customization specification.

2. Use a script which I just find at: https://www.joeydegraaf.net/provision-a-full-virtual-machine-pool-in-specific-ou/