A Microsoft cloud service that enables deployment of Azure services across hybrid and multicloud environments.
Assuming you mean the Azure Arc ESU license resource: this is expected today. Windows Server 2016 remains in extended support until January 12, 2027, so it is still receiving normal security updates.
Azure Arc ESU licensing currently covers Windows Server 2012 and 2012 R2, which is why only those versions appear. Microsoft has not announced an Azure Arc ESU enrollment date for Server 2016, so there is no agent, provider-registration, or portal setting that will make it appear yet. Continue normal patching and upgrade planning, and watch the product announcements as 2016 approaches end of support.