Mobs spawn in Nether

Status
Works as designed
Type
Product/platform
Not applicable
Priority
Normal
Issue description

Is it normal that Custom mobs, spawn in Nether? I found my custom spider and zombie spawning in nether (They don't have restricted biome and they are Monster type)

Issue comments

If you don't limit mob spawning and the type is monster, it will spawn in nether too by default.