Primitives nuget library reports missing properties

[BryanAldrich]

The ServiceModel.Primitives library (8.1.2 at last check) has a lib and ref copy of the DLLs. I have noted that these are missing some properties (in my case, OperationContext.InstanceContext).

The MS docs https://learn.microsoft.com/en-us/dotnet/api/system.servicemodel.instancecontext?view=net-9.0-pp for InstanceContext says that it includes an OperationContext property for .net8/9, however, that property cannot be found by the compiler (msbuild or dotnet).
To make things more confusing, the ILSpy plugin for visual studio decompiles the lib/ copy of the DLL, yet VS uses the ref/ copy to compile.

To Reproduce

1. This small project targets net472 and net9. It does not compile despite the docs saying it should.

test.zip

Expected behavior
Compilation.