This is just a quality of life thing.
I have a great deal of sounds parented inside a SoundGroup – and for each of them, I also have to manually set their SoundGroup property to their parent.
I was confused by this behavior when I first used SoundGroups because originally I thought just being parented to the SoundGroup meant that the SoundGroup applied to them, but that’s not the case and left me a little annoyed after debugging an issue that was caused by the sounds which weren’t actually in the SoundGroup.
As for implementation, I don’t really care if this automation happens during runtime or in the editor. Having it happen during the editor might be best so it can be customised by developers further, however during runtime might be more convenient if people are creating sounds with scripts.