Well Eddie maybe what this theory of yours is saying it makes sense,but I also had a thought that in God of war 2018 when Atreus heard her is because he can't accept the fact that she is gone and kratos had accepted that she's dead and will not come back,and in God of war Ragnarok I think it was opposite Atreus accepted his mom is gone but kratos heard her in alfheim because he sort of misses her,then Atreus tell him she's gone. That was my thought. But hopefully answers will be revealed one Day.