Currently you can set capacity so that remaining estimates are applied as completed work when a feature is set as shipped.
However, when importing from JIRA (or CSV) an imported feature to an active release that is marked as shipped does not apply it's capacity as completed work.
This makes it so customers have to go through and unship/re-ship features to get the capacity to apply.
Thank you for the idea. Given the current work around and historical support for this idea, we are unlikely to make changes here at this time. We hope you can understand.