I have to admit that I find this KB article and support statement to be quite baffling. It states that:
Moving a virtual machine (VM) from a Windows Server 2012 R2 Hyper-V host to a Windows Server 2012 Hyper-V host is not a supported scenario under any circumstances.
When you try import a VM that is exported from a Windows Server 2012 R2 Hyper-V host into a Windows Server 2012 Hyper-V host, you receive the following error message:
Hyper-V did not find virtual machines to import from the location <folder location>.
The operation failed with error code ‘32784’.
I am going to raise this with the product group. I see it as a genuine issue because anyone doing an upgrade-migration will require a rollback plan that will work and is supported.
You can move a VM from a Windows Server 2012 Hyper-V host to a Windows Server 2012 R2 Hyper-V host. This is a supported scenario and cane even be done with zero downtime using Cross-Version Live Migration.