If it doesn't automatically uses ios reload (I think it doesn't), it's the ios used by system menu since preloader doesn't touch the tmd of the system menu...
boot2 boots the ios that will be used by system menu and that's no different for preloader... so initially takes the system menu's ios when booting but of course afterwards it can reload another ios which in preloader v0.29 you can do that reloading with preloader's settings...