Sink Writer Audio Streams Limit

Hi,

I have a question regarding the streams limits of the Sink Writer.
I'm trying to add multiple audio streams to the Sink Writer and it fails after the first one.
I'm using MFCreateSinkWriterFromURL and passing a mp4 file path.
I'm guessing that function creates a mp4 Media sink and I've tried creating a MP4 Media Sink using MFCreateMPEG4MediaSink() but the number of streams are fixed.
The doc says The MP4 media sink supports a maximum of one video stream and one audio stream.

Is there a way to easily achieve this?
How come this does not support multiple audio streams?

Thank you,

Francis