Census has always allowed you to create relationships through a sync (e.g. between a Contact and an Account).
For example, when we sync the contact email@example.com, it gets attached to the Census Account in SFDC. However, previously if in your application database or any other sources you wanted to break that relationship, we wouldn't break that relationship in SFDC.
Now, when we see a
null value in the mapping key of the associated object, we will remove the relationship for you in Salesforce.
If you have any questions, let us know