Curious if you tried to modify -unreclaimed-space-threshold to see if space would reclaim faster. If not could you try it?
(advanced privilege level)
Command: storage aggregate object-store modify with the -unreclaimed-space-threshold
Fabric Pool Documentation: Page 18 / 52 "Object deletion and defragmentation" https://www.netapp.com/media/17239-tr4598.pdf?v=120202193912P
Command Documentation: https://docs.netapp.com/us-en/ontap/fabricpool/commands-manage-aggregates-reference.html
This optional parameter specifies the usage threshold below which Data ONTAP reclaims unused space from objects in the object store. When Data ONTAP writes data to the object store, it packages multiple file system blocks into one object. Over time, blocks stored in an object can be freed, leaving part of the object unused. When the percentage of used blocks in an object falls below this threshold, a background task moves the blocks which are still used to a new object. After-wards, Data ONTAP frees the original object to reclaim the unused space. Valid values are between 0% and 99%. The default value depends on the object store's provider type. It is 20% for AWS_S3, 15% for Azure_Cloud, 40% for Azure_Stack, and 40% for SGWS.