Docker Windows runner and Windows Server 2019 LTSC not supported?

I have a Windows Server 2019 Datacenter Edition server which seems to be compatible per the documentation here:

However when running a build it seems it is not:
ERROR: Preparation failed: detecting base image: unsupported Windows Version: Windows Server 2019 Datacenter

From what I can tell it seems the version check is expecting the Semi-Annual Channel (SAC) build number to be in the version string i.e. 1809, 1903, etc.

But the Long Term Supported Channel (LTSC) doesn’t put the build number in the version string even though it is 1809 build.

Is this a bug? Have others had any success with this?

It seems really strange to only support the SAC builds and not the released version of Windows 2019.