As CS25771 states Checkin/Dissociate CADDocument with a WTPart iterates the WTPart for Image link in Windchill PDMLink
Customers need the ability to set the ability to checkin the CADDoc without iterating Part.
Now they can associate it without iterating. And if they never have checked the CADDoc in they can dissassociate. But they also have the need of having a setting for been able to checkin a image-linked CADDoc and also dissassociate it without the Part getting iterated.
If you have a multiple linked Part and one has an Owner-link already you in most use cases whants to be able to change the multiple image-linked CADDocs without iterating the Part that has its owner-link to CADDoc.
In that case only the owner-linked CADDoc should iterate the Part and all the image-linked CADDocs shouldnt.