register_entity_type and search

Hi,i'm using elgg 1.7.1. I've created a new subtype and i don't want that elgg search find it.
at the moment i haven't register the entity type with register_entity_type, so search doesn't find that subtypes.

don't register the entity type lead to some unwanted side effects or it's the correct way to do that?

thanks in advance
Luca