I think the general concensus is that the ISH is an aspect the DOES seem to know everything and is the one who can help the T understand the most. It doesn't have to be a protector at all... but a record keeper. Also, it is generally accepted that most nearly everyone with DID has some fashion of an ISH. Maybe the "protector" aspect of it is that this part might not allow the T to have information right off the bat.. not til the trust is built, etc. imo