I'd like to see in the future more mob sounds, espiecially for shivers. I imagine doing something in the dark and in one moment I get shivers down my spine by shiver's scream indicating it saw me and is ready to attack me.
This could work for both: signal that shiver saw the player and one more way to scare the players when they doesn't expect that.
You can add lore to why shivers scream and doesn't try to stealth you, for example they still have human side and try to warn you or just scream like other animals because of primal instinct, it's up to players and theorists.