no not all alters are created by the body born or out of dissociation due to trauma....

one example of an alter that is not a dissociative type alter is one that is an hallucination alter...

one that medication induced alter,

one that is psychosis induced, another one a false alter induced due to therapist induced....

I have a friend who has schizophrenia, when his meds are off track and his schizophrenia symptoms are active he hears voices and has alters that tell him to do mean things. tells him people are out to get him...

I know someone else who created false alters (a type of non DID type alter.) in order to please their treatment provider...

another non dissociative type alter in my location is commonly called invisible friends...

my point there are many different kinds of alters....