I see what you are getting at...here in my location this does not mean a baby doesnt have an "original" or birth personality.

here in my location a self is not an alternate personality. the self is the sum of that persons consciousness and unconsciousness, memories, experiences, thoughts feelings, emotions, all of this combined makes up a persons self..

example of a self in a new born baby would be what they see when they are born, what they hear when they are born what they dream about, what they think about. being hungry, being wet, ...the brain controls all of this through electric impulses. all these things together forms that baby's "self" under normal situations babies ....learn ...how to regulate (control ) these things

now lets add the link information...

when a baby doesnt bond\attach to their parents, because of going through trauma it affects how they react, think, dream,..in short they have learned to regulate a different way.

this in turn causes the human being (in this case a baby) to dissociate \shut off\shut down (the text word for this in the link is truncation)

this leads the human being (in this case the baby) to switch into and out of each of their parts of self (what I listed above) but because of the trauma each of these parts of self are now dissociated from each other, no longer connected.

as the human being continues to use their dissociative skills those parts of self eventually evolve into alternate personalities.