I realize that there is now a warning box when checking "fault tolerant" mp4 recording. My question is, since audio will get out of sync every single time its used, what possible workflow would this ever be useful? Not recording audio maybe? Anything else?

Why not replicate what OBS did to achieve fault tolerance? Record to mkv then remux the file to mp4 afterwards? No transcoding required and you get all the benefits of mp4 with none of the dangers of uncompleted or corrupted files.