RDS CALs installed on WVD Session Host

Hello,

We're evaluating WVD for a number of different clients to migrate them from a traditional RDS deployment, into WVD. A lot of our clients are trying to achieve a full "serverless" environment, trying to avoid IaaS resources as much as possible. In one scenario, we were hoping to deploy a single Azure VM to server as WVD Session Host for RemoteApps. It is joined to AzureAD Domain Services. And for this scenario, we're not looking for scalability so we're not using the template/image process. Just joining the session host as-is into the existing host pool (it being the only server in the pool), in order to leverage Azure/WVD as the RDS front-end. 

All of this seems to work just fine, however it appears we're running into an issue with installing licensing. The RDS Licensing role was installed prior to joining the server to WVD, but the CALs were not installed. Now that the server is a part of WVD, it appears we are unable to install licensing onto it (being told the option is greyed-out).

SO the question is this, does WVD block the ability to install RDS CALs directly onto a WVD Session Host? Is it a requirement to have RDS licensing on a separate server? If not, then I may attempt to remove from WVD, install licensing, and add it back.

Or is WVD unrelated and we are running into some other issue I need to troubleshoot?