Currently, the toggle doesn't include the Deep Dark biome or account for non-hostile spawning biomes added with custom world generation data packs.
Of course, the custom biome aspect may be more of a hurdle that's not worth enduring, but it would only make sense to include the Deep Dark biome to the toggle as hostile mobs cannot naturally spawn in the biome.
Currently, the toggle doesn't include the Deep Dark biome or account for non-hostile spawning biomes added with custom world generation data packs.
Of course, the custom biome aspect may be more of a hurdle that's not worth enduring, but it would only make sense to include the Deep Dark biome to the toggle as hostile mobs cannot naturally spawn in the biome.