Still would not agree that "Exception is going to be mostly inland applicants that were out of status at time of applying." That seems like a bold assumption for the `mostly' applicants without status, but...it's your valid opinion.Approval in principle comes after the check of relationships , so your reset is after the important part. But perhaps I've misunderstood your point.
Logic very simple: persons out of status have motive to pursue spousal sponsorship for fraudulent reasons. Persons in status have far fewer reasons to do so. Interview is one mechanism to check relationship bona fides.