For SkySat collections, the Unrectified Asset tag displays when the ground control ratio is less than 1 meter. For more information, visit the Planet developers documentation.
The Unrectified Assets tag displays when Planet imagery is unable to align the imagery or rectify it because of limited ground control. The data can still be useful given the limited ground control points.
For other item types we use the ground control metadata which is a boolean expression. To check the metadata of an individual item and see the value of the field, click i.