Well, you’ll never get an authoritative answer in this forum because we’re all users and not Microsoft.
Yes you can use a Windows OEM System Builder license on a VM.
You would have to be careful if you move the VM around, as the OEM license is tied to a single system. For a VM, that’s the VM’s virtual hardware and associated things like the VM’s BIOS UUID - which do differ in many respects from the host. Moving a VM and answering that you copied it (not moved it) may change the virtual hardware enough that Windows will think it’s on a new machine and therefore in violation of the licensing.