FND_USER.PERSON_PARTY_ID

I have noticed that after merges FND_USER.PERSON_PARTY_ID refers to an inactive party_relationship. It is  the subject_id  of the (old) merged party relationship. The new party relationship uses a new person party. Why is customer_id updated while ther person_party_id is not when the merge occurs?

I encountered issues when attempting to use Note:

How To Delete Active iStore Shopping Cart For An User (Doc ID 1261926.1)

select customer_id from fnd_user where user_name = <iStore username > ==> value 1

select person_party_id from fnd_user where user_name = <iStore username>

select object_id from hz_relationship where subject_id = <