Creating a Deal through API does not autopopulate org when assign person_id

I am trying to Add A Deal through the API. If I assign an organization, it does not seem to auto populate the contact person. If I instead assign a person, it does not automatically auto populate the organization associated with the person.

So if I create the deal and pass person_id and org_id, do I need to make sure it is a person belonging to the org_id? Will it be overwritten or have conflict at some point?