Do you see them used in some generated code?
No, I didn't see any example of how to allocate the buffer in MIDL_STUB_MESSAGE. It's just my best guess that NdrOleAllocate is meant to be used here.
there appears to be a mismatch with what NdrClientInitializeNew() would use for memory management pointers, and what test would use in this explicit allocation
You mean that it's odd that these buffers aren't allocated with pfnAllocate and pfnFree? That was strange to me too. I added some tests to confirm that NdrGetBuffer and NdrFreeBuffer don't use pfnAllocate and pfnFree either.