primary identity in Real-Time Customer Profile and identity graph
There is a note in this document:
A single schema may have many identity fields defined, but can only have one primary identity. All identity fields (primary or otherwise) contribute to the identity graph for an individual customer, but Real-Time Customer Profile uses only the primary identity as the source of truth when merging data fragments together. If you want to enable a schema for use in Profile, the schema must have a primary identity defined.
I didn't understand this note. Isn't the profile merge of the Real Time Customer Profile built based on the identity graph? Why do these non primary identities only participate in the identity graph but do not affect the profile merge?
Regards