Windows 10 Edition Uplift to Enterprise on OEM Activate Systems

We are receiving machines from an OEM that are Windows 10 21 H2 Professional and activated with an OEM license for same. These then get hybrid AzureAD joined to our ADDS domain and AzureAD tenant. Users then sigin into them with their ADDS creds. These users also have the full M365 E5 license and hence the Windows 10/11 service plan. 

What we have found is the following:

1. The system does not uplift the Edition to enterprise. 
2. If we build a VM that has the KMS client activation code and do the same the edition does get uplifted

Reading here I would have thought that the OEM machine would uplift? Any ideas on if this is the case or how to troublehoot?