You're extrapolating. Those aspects aren't part of the matter. There's nothing about these people that indicates they want to be alone. Making a tulpa literally depends on the person's desire for companionship, not their desire to be alone.
That is, the steps of the schizoid personality is:
1. Loneliness
2. Escapism in the form of internal fantasy
3. Choosing to be alone, because the internal fantasy is judged to be enough