Cannot set custom SEI using Media Foundation h264 encoder

Question

I have set up a MFSinkWriter that takes a RGB MFMediaType in input and generates a H.264 MFMediaType as output. I need to add SEI information for every MFSample that is encoded. Is it possible to achieve this? What is the intended use of MF_MT_FORWARD_CUSTOM_SEI for the output MFMediaType?