As a prerequisite, Fusion supports playback and rendering only for specific WAV files, not other audio files or audio included in video files.
Even in Resolve, there is no audio button on the Fusion page in the first place, and when creating a Fusion Clip from a video clip on the Edit page, the audio track is separated at that moment. So when I want to strictly synchronize the sound and the graphic, I have to make some kind of mark (cigarette burn or text continuity) separately and work on it.
So I totally agree with this post and have requested the following since Fusion 9:
-Loader node (and now, MediaIn node is also), added the function to read audio files and data in video.
-Function to transfer the above data to Saver (and MediaOut) node.
-Audio waveform display in subV or time ruler etc.