I don't know if the spawn protection only affects the main world or all wordls.
That may also depend on the multiworld plugin you use.
You can also protect it manually using worldguard or something like this.
Hello. How to add WorldGuard plugin to the server? I checked all manuals but did not find actual answer with working examples (for example, a lot if internal URLs inside the aternos.org domain are not actual anymore).
Thanks