I can confirm that such kos objects are rarely supported. I know some vendors who have implemented it and tested it successfully at the IHE Connectathons, but in real world at the customers there implementations are not active.
If you do not want to delete but to correct it (eg there is a badly windowed image sent and you want now to send a better image and delete the old one), it often works fine to send the new image with exactly the same UIDs like the old image. this is faulting dicom, but it works on many pacs systems.