Hi @chriskk - I found the same here - Understanding correlation rule, correlation configuration, and default correlation - Compass (sailpoint.com)
In general, we should do the aggregation based on some unique not null attribute on Sailpoint side rather than doing it using some attribute whose data is null.
We never faced such kind of behavior when we are doing the correlation based on some unique not null attributes. If the criteria don’t match then it will create an uncorrelated account, else if you want that this should not happen then we mark the below option to restrict SailPoint to create uncorrelated account.
Thank you!