Those would only work for audio files inserted as <audio> tags instead of Anki’s native [sound:...], which makes it less convenient to add and harder to manage, since one will have to rename all files, adding underscores, and manually keep track of which files in the collection are used and which ones are not.
Yeah, this kind of threads seems to converge to the same kind of solutions each time 
:Selective autoplay of audio for certain notes - #22 by Eltaurus